HK1184743B - Ash and solids cooling in high temperature and high pressure environment - Google Patents

Abstract

Disclosed are cooling and depressurization system equipment, arrangement and methods to cool solid particles from a coal gasifier operating at high temperature and pressure. Ash from the coal needs to be continuously withdrawn from a circulating fluidized bed gasifier to maintain the solids inventory in the gasifier. The system disclosed enables use of conventional materials of construction for heat transfer surfaces. The supports for the cooling surfaces are located on the lower temperature upper section of the primary cooler. The cooled solids along with the fluidizing gas exits the primary cooler to a secondary receiving vessel where the solids can be further cooled by conventional means. The fluidizing and entrained gas entering the secondary vessel is filtered and vented through a vent pressure control valve. The column of cooled solids in the secondary vessel is depressurized by a continuous depressurization system to low pressures which are sufficient for conveying the solids to silos for disposal. The system and methods proposed are equally applicable to many high temperature, high pressure processes that require cooling and depressurization of process solids.

Description

Cooling ash and solid particles in high temperature and high pressure environment

Cross Reference to Related Applications

This application claims the benefit of U.S. provisional application No. 61/372,008, filed on 9/8/2010, the entire contents and substance of which are incorporated herein by reference.

Background

1. Field of the invention

The present invention relates generally to cooling of solid particles from applications operating at relatively high temperatures and pressures. And more particularly to cooling of high temperature ash from coal gasifiers operating at temperatures in the range of about 1500F to 2200F and pressures in the range of about 30 to 1000 pounds per square inch absolute (psia).

2. Description of the related Art

Cooling of hot solid particles in a gasifier or reactor operating in a temperature range of about 1500 ° F to 2200 ° F, and a pressure range of about 30 to 1000psia presents a number of challenges, any of which have not been fully overcome by conventional systems.

The first challenge is to support multiple heat exchanger tubes that exchange heat from the solid particles to the cooling medium. The difficulty in this problem is that the stent must be anchored to the outer wall, requiring penetration through the layer of refractory material necessary to resist erosion due to movement of solid particles (mass mean diameter ranging from about 50 to 400 microns in size) and to insulate the outer wall from overheating.

The ventilation gas used to assist the movement of the hot particles and the flow of the particles over the cooling surface can cause vibrations in the cooling ducts and the support. Such vibration of the brackets can damage the refractory material and locally overheat the vessel wall. Thermal conduction through the bracket can also overheat the vessel wall, causing damage and deformation to the vessel. This is a significant concern when the vessel forms a pressure boundary.

A second challenge in the development of high pressure, high temperature heat exchangers is achieving proper control of the flow of solid particles to the heat exchanger without interfering with the operation of the gasifier or reactor into which the solid particles are being withdrawn and/or cooled. Also, with the circulating fluidized bed gasifier, the blowing gas is not returned to the water storage tower or the gasifier as it is pressure limited when the solid particles are withdrawn from the standpipe. The return of the blowing gas through the take-off point prevents the flow of solid particles to the cooler. The treatment of the exhaust gas is difficult because the gas entrains particles at high process temperatures. In these cases, the challenge becomes how to expel the blast gas and a portion of the gas entrained by the solid particles.

A third challenge is to optimize the design of the cooler so that when the solid particles in the cooler are in contact with these heat conducting surfaces, there is a temperature range from about 800 ° F to 1000 ° F. Such considerations improve the reliability and durability of the heat conducting surface of the cooler and facilitate the use of low cost steel for the cooling surface. While the solid particles at the inlet of the cooler have a temperature range of from about 1500 ° F to 2200 ° F as they are withdrawn from the gasifier, a robust cooler design forces the solid particles in contact with the heat transfer area to have a temperature of less than about 1000 ° F. Known exchanger designs have one or two tube sheets that support the heat exchanger tubes. Tube sheet diameters tend to be large diameters in commercial coolers. It is advisable to design the cooler so that the tube sheet is not exposed to the hot solid particles.

A fourth challenge in chiller plant design relates to proper handling of foreign and extraneous materials originating from or passing through the gasifier. Foreign and extraneous materials in the process may be formed, for example, by: contaminated feed materials, cracked refractory materials, broken gasifier internals and slag lumps, and slag formation during processing due to variability in the feed fuel (e.g., coal) or illegal handling. These materials are often oversized and need to be removed from the process before reaching the heat exchanger surfaces in order to limit or prevent the flow path of the hot solid particles from being blocked.

Conventional systems for cooling hot solid particles from a reactor are mainly divided into two application areas: cooling hot solid particles (catalytic particles) from a Fluid Catalytic Cracking (FCC) process and from a circulating fluidized bed (CFB combustor) boiler.

In the FCC field, examples include U.S. Pat. No. 4,424,192 to Lomas (Lomas) et al, U.S. Pat. No. 4,425,301 to Vickers (Vickers) et al, U.S. Pat. No. 4,822,761 to Walters (Walters) et al, and U.S. Pat. No. 5,209,287 to jensen (Johnson) et al. These teachings are applicable to relatively low pressure processes, such as FCC processes that typically operate below about 50 pounds per square inch (psi). In these examples, jensen (Johnson) et al disclose the use of a shield to prevent extraneous materials from entering and interfering with cooler operation. However, as will be appreciated by those skilled in the art, with gasifier operation, it is highly desirable that extraneous materials can be discharged from the gasifier, as the extraneous materials accumulated in the gasifier can cause a variety of operational problems, including the formation of slag lumps in the gasifier.

The FCC design includes: hot solid particles enter the cooler from the top and cooled solid particles exit from the bottom or from the side of the vessel near the bottom. Thus, these references disclose systems that require gas velocities high enough to fully fluidize the particles in the bed to ensure that the bed reaches a uniform temperature. This is not a problem in FCC processes because the size of the catalyst particles is relatively uniform and it is relatively easy to achieve uniform fluidization over a narrow range of gas velocities.

As those skilled in the art will recognize, this situation is quite different in gasification and combustion processes, where particle sizes can range from approximately 30 microns to 10,000 microns, and the full fluidization velocity in the cooler must be close to the minimum fluidization velocity of the largest particle size in the cooler. For 10,000 micron particles, the minimum fluidization velocity can be as high as about 10ft/s, and operation at such high velocities requires a large gas flow through the cooler. It is difficult to flow such a large amount of gas through the cooler back to the gasifier or combustor without interfering with its normal operation.

Another problem with the FCC reference is that if the common extraneous materials in gasification and combustion processes pass through the cooling bundle, they can separate and accumulate at the bottom of the cooler, which can eventually interfere with the proper operation of the cooler due to the FCC design with the solid particles flowing down and being withdrawn sideways near the bottom. It is difficult to apply these teachings to cool gasifier solids having a broad particle size distribution, such as solids from a fluidized bed or circulating fluidized bed gasifier.

In the CFB art, examples include U.S. patent nos. 5,510,085 and 5,463,968 to arabinity (Abdulally), 5,184,671 to allisson et al, and 7,194,983 to kokuku (Kokko). In these teachings, both the solid particles and the fluidizing gas are returned to the combustion chamber to maintain the combustion temperature. When these references disclose ongoing coolers, the exterior surfaces of the cooling tubes are in substantial contact with the solid particles, which have a temperature near the combustor operating temperature of about 1600 ° F. While such operating temperatures necessitate the use of expensive alloy materials for the heat exchanger, the overall environment is tolerable for most alloy engineering materials. However, those skilled in the art will recognize that for gasifier operation, operating temperatures may be as high as about 2000 ° F, and thus, when hot solid particles directly contact the heat transfer surface at such high temperatures, material selection may be a challenge or material costs may be high.

Furthermore, other CFB examples cited, besides Kokko, ignore the deleterious effects of extraneous materials entering the heat exchanger. Kokko (Kokko) recognized the importance of avoiding solid particles passing through certain parts of the heat conducting surface and devised a way to ensure that solid particles flow across the entire heat conducting surface. However, in the design of Kokko (Kokko), the solid particles have to be turned in three chambers, which naturally makes the flow of the solid particles more complicated and makes it more difficult to handle irrelevant materials.

U.S. patent No. 7,464,669 to Maryamchik et al discloses a ash cooler having two chambers, one for coarse ash discharge and the other for fine particle discharge. However, the large particle ash chamber does not have a cooling surface and therefore the ash being withdrawn from the chamber is at substantially the same temperature as the ash in the combustion chamber. It is also difficult to achieve good separation of coarse particles from fine particles in a fluidized bed. In Maryamchik et al, the fluidizing gas is returned to the combustion chamber, a practice that may be undesirable for some applications.

Furthermore, Maryamchik et al disclose that a bundle of pipes for cooling the solid particles penetrates the refractory wall. This practice is not a major problem for CFB boilers, as the combustion chamber operates substantially near atmospheric pressure. Due to this low pressure operation, even if there is damage to the refractory material, catastrophic failure of the vessel wall does not occur. However, it will be appreciated by those skilled in the art that for gasifier operation at high pressure, the cooling surface through the wall can become a serious safety issue and there is no other known solution than to avoid this arrangement altogether. Furthermore, the cooling surfaces in the heat exchanger will still be in contact with the fine particles at high temperatures of about 1600 ° F, which is essentially the same as the combustion chamber, thus necessitating the use of expensive engineering alloy materials for the heat transfer surfaces.

U.S. patent publication No. 2009/0300986 to Liu (Liu) et al discloses cooling the gasified ash from a fluidized bed gasifier. In Liu (Liu) disclosure, extraneous material is screened out at the entrance of the cooler and collected in a separate container. In this configuration, substantial recycle gas must be used to blow the small particles away from the extraneous material. Substantial recycle gas must be used to prevent small particles from entering the solid particle cooler and also to continuously purge the shield to ensure that it remains free of blockages. This large purge gas flow in combination with the handling of high temperature particles increases material costs, manufacturing costs, and operating costs.

In Liu (Liu) disclosure, all purge and fluidizing gas flows back to the gasifier, preventing operation if such flows are excessive. In addition, the cooling surfaces of Liu (Liu) run through the refractory material of the cooler and the vessel wall, which makes the cooling wall design potentially difficult. Even if the operating pressure of the gasifier is less than 50 psig. During operation, the cooling surface contacts solid particles, which approach the operating temperature of the gasifier, resulting in a challenging and expensive design.

What is needed is a cost effective and reliable solution for cooling high temperature, high pressure ash from a gasifier, and other similar applications. The present invention is directed primarily to such systems and methods. The present invention overcomes the various challenges previously discussed and provides a system for cooling high temperature ash from a coal gasifier operating in a temperature range of about 1500 ° F to 2200 ° F, and a pressure range of about 30 to 1000 pisa.

Brief summary of the invention

The present invention, in its preferred form, briefly describes an effective solution to the various problems discussed previously with respect to the removal and cooling of high temperature ash from a high pressure operated gasifier. The applicability of the present invention to gasification processes is described, but one of ordinary skill in the art will recognize the general applicability of the present invention to many processes that require cooling and the withdrawal or return of high temperature, high pressure solid particles to the process.

In exemplary embodiments of the present invention, the fluidizing gas used in the ash cooler is not returned to the gasifier for both process and safety reasons. Also, in the present invention, these solid particles are withdrawn from the gasifier into an overflow pipe lined with refractory material and having a U-shape at the bottom of the pipe. In this configuration, the solid particles enter the primary cooler from the bottom center and flow upward into the fluidized bed. The fluidizing gas flows upward with the solid particles and exits the top of the cooler.

In one embodiment of the invention, due to the physical arrangement of the cooler, the cooler solid particles in the fluidized bed will be intended to flow down the wall and mix with the new hot solid particles entering from the gasifier, thereby lowering the temperature of the solid particles before they reach the cooling surface. These solid particles in the fluidized bed are mixed back and circulated internally as a whole, thereby generating a vertical flow. Such as Zenz, F.A and Othmer, d.f. et al (1960, fluidization and fluid particle system, page 290-.

The cooler solid particles circulating internally within the fluidized bed mix with the hot solid particles from the gasifier and the mixture temperature will be below 1000 ° F. The internal solids circulation rate in the fluidized bed and the resulting mixture temperature from the mixed hot and cold solids depend on the superficial gas velocity used to fluidize the solids in the cooler, the bed density, the solids characteristics, and other factors. By adjusting the superficial gas velocity to between 0.1 and 3ft/s, the internal cooler solid particle circulation rate and solid particle mixture temperature can be controlled to a desired temperature before the solid particles of the mixture contact the heat transfer tubes.

In a preferred embodiment, the shape of the cooler bottom is conical. Along the edge of the cone, nozzles are installed to inject blowing gas into the cooler to fluidize the solid particles. The fluidization velocity is determined primarily by the size and size distribution of the solid particles and the temperature of the solid particles from the gasifier. The minimum gas velocity required is about 0.1ft/s greater than the minimum fluidization velocity that can be experimentally calculated or determined by one skilled in the art of gas-solid particle fluidization phenomena.

In a preferred embodiment, the space or volume between the inlet for the hot solid particles at the bottom of the cooler and the bottom tips of the cooling tubes within the fluidized bed should be such that the hot solid particles entering the cooler have sufficient time to mix with the relatively cooler back-flowing (internally circulating) solid particles from above. Normally, for solid particle sizes in the range of 0.1 to 10mm, the residence time of the solid particles in this preferred space should be in the range of 10 to 200 seconds.

The heat transfer surface may be a bundle of many kinds of tubes. In a preferred embodiment, this tubing arrangement is in the form of a bayonet tube (bayonet tube). In this type of heat transfer surface, each heat transfer tube arrangement actually comprises two concentric tubes, an inner tube and an outer tube. The inner tube is used as a conduit for the flow of water under gravity from the steam drum. The water is warmed in the annular region between the inner and outer tubes. A two-phase mixture of steam and water flows through the annular space by buoyancy and collects in the space above the tube sheet near the top of the cooler before flowing back to the steam drum.

In a preferred embodiment, cooler solid particles in the temperature range of 400 to 600 ° F overflow through an outlet nozzle located directly below the tube sheet. In this arrangement, cooler solid particles rarely contact the tube sheet located near the top of the cooler. The tubesheet need only be designed for the exit temperature of these cooler solid particles, which will be below 600 ° F. And, these external bayonet tubes only contact solid particles below 1000 ° F. Thus, no expensive alloys are required for the materials of construction of the tubes and tubesheets. The solid particles in contact with the cooling conduits are further cooled and the solid particles in the upper portion of the cooler are typically cooled to an exit temperature in the range of 400 to 600 ° F while the bed is fluidized. Since the tubes are supported by the cooler tube sheet, the problems associated with supporting the cooling tubes are eliminated.

Other types of tube bundles may also be used in the solids cooler. When the cooler is handling high temperature solid particles, it is essentially a refractory lined vessel. It is preferred that the different forms of tube bundles that can be envisioned are fixed near the top of the cooler so that the fixing or support of the tube bundle is not subjected to high temperatures. Since the cooler roof is in the low temperature region, the use of a refractory lining in the freeboard area (freeboard region) to protect the vessel walls is unnecessary. In such preferred embodiments, potential damage to the refractory material by the duct support can be prevented by completely eliminating the refractory material for other types of tube bundles and supports in the freeboard area.

To further reduce vessel size and cooling costs, the cooling surface treats the normal solid particle flow rate. In applications where the maximum flow rate of hot solid particles is much higher than normal for a short period of time, the arrangement made in this embodiment is to provide additional cooling by spraying atomized water droplets in the conical section of the vessel together with a blowing gas.

The fluidized bed with the mixture of hot solid particles and cold solid particles is contacted with the tube bundle and cooled to the desired design temperature. The solid particles have a generally upward flow direction and are withdrawn through a nozzle or nozzles in the upper portion of the cooler vessel. If bayonet tubes are installed, these solid particles are withdrawn from the side wall of the vessel and directly below the tube sheet as shown in FIG. 1. The lateral extraction maintains the strength and integrity of the tubesheet. If other types of tube bundles are used, it is not critical to remove these solid particles from either the side walls or the top of the cooler vessel.

In a preferred embodiment, the solids withdrawn from the high temperature primary solids cooler flow into a secondary cooler for further cooling. The secondary cooler provides additional cooling surface to cool the solid particles to the desired exit temperature. The ash from the gasifier is typically cooled in a secondary cooler to an exit temperature in the range of 200 to 350 ° F. The secondary cooler is a vessel lined with inexpensive non-refractory material with conventional cooling surfaces, since it receives cryogenic solid particles typically in the range of 400 to 600 ° F for further cooling, and one skilled in the art can speculate on a suitably cryogenic cooling design.

The fluidizing gas for the first cooler is discharged from the top of the secondary cooler through a filter section that prevents the release of entrained fine particles into the blowing gas stream. The flow of dust-free ventilation gas is regulated by a pressure regulator in the ventilation line which maintains the desired pressure in the secondary cooler and also in the freeboard area of the primary cooler. By adjusting the pressure differential between the gasifier and the secondary cooler in this embodiment, the flow rate of hot solids from the gasifier to the bottom inlet of the primary solids cooler can be controlled.

These cooled solid particles are withdrawn from the bottom of the secondary cooler. The continuous depressurization system reduces the solids pressure from an operating pressure in the range of 30 to 1000psi to an exit pressure sufficient to transport the solids to a silo for disposal or other downstream processing. By causing U.S. patent publication No. 2010/0266460, which is incorporated herein, to describe a continuous depressurization system having pressure reduction devices that facilitate pressure reduction of the solids stream from the operating system pressure to the pressure required for downstream processing.

In another embodiment of the invention, when the tube bundles are not bayonet type, a filter section may be installed on top of the primary solids cooler. These solid particles can be discharged directly to the continuous depressurization system if sufficient cooling can be achieved in the primary cooler to meet the process requirements. In such an embodiment, a secondary cooler becomes unnecessary.

In an exemplary embodiment of the invention, a system for cooling ash and solid particles from a high temperature and high pressure coal gasification environment is provided, the system comprising: a downcomer connecting the gasifier and the primary solids cooler and directing the solids to the bottom of the conical cooler vessel; a cooling surface inside the primary solids cooling vessel for exchanging heat between the solids and a cooling medium; a rack near the top of the vessel for cooling surfaces or cooling beams; a solids outlet near the top section of the primary solids cooler vessel; a gas-solid particle separation system at the inlet of the secondary cooler; a vent filter section near the top of the secondary cooler to prevent entrained fine solid particles from entering the vent line; a pressure control vent valve for controlling a pressure differential between the solids cooler and the gasifier; a secondary cooler (or receiver vessel) to further cool the solid particles or to act as a buffer tank for a continuous depressurization system; and a connected pressure reduction system for reducing the operating solids pressure to a level required for discharge.

The system is capable of cooling and depressurizing ash or solid particles from a gasifier or reactor operating in a temperature range of about 1500 ° F to 2200 ° F, and a pressure range of about 30 to 1000 psia. The connected downcomers and primary solids coolers may be lined with refractory material to withstand corrosion and high temperatures.

The conical region and volume below the cooling surface can be designed to be large enough so that the returning cold solid particles have sufficient time to mix with the entering hot solid particles. The cooling surface of the primary cooler may be a bayonet-type cooling conduit, the outer conduit of which is exposed to below about 1000 ° F of the fluidized bed of solid particles. Omega-shaped springs may be attached to these inner bayonet tubes to minimize tube vibration.

The shelves of the cooling surface may be located in a low temperature section of the upper portion of the cooler where the maximum temperature experienced by the support material is below 600 ° F.

The hot solids exiting the gasifier may be at a higher elevation relative to the cooler solids exiting the primary cooler. Due to the hydrostatic head caused by the difference in elevation, excess hot solid particles from the gasifier may be withdrawn, cooled, and depressurized for disposal.

Blowing air may be added to the downcomer-connected conduit to control the flow of solids due to hydrostatic head created by the difference in elevation. The blowing rate can be adjusted such that the blowing gas flows downwards together with the solid particles to avoid disturbing the operation of the gasifier or reactor. Control of the solids flow can also be regulated by balancing the pressure differential between the gasifier and the cooler vessel with a vent pressure control valve.

By sufficient ventilation in the bottom conical section of the primary solids cooler, extraneous material from the gasifier can be separated from the hot solids.

The incoming hot solids may be mixed with cold return solids from above inside the primary cooler before the solids mixture contacts the cooling surface to maintain the solids mixture temperature below about 1000 ° F.

The fluidizing gas exiting from the primary cooler vessel with these cooled solid particles can be filtered and the clean gas discharged to downstream processing.

The secondary vessel may receive solid particles from the primary cooler for further cooling, and these solid particles may flow downward by gravity and exit through the bottom of the vessel.

The cooled solids may be withdrawn from the secondary vessel via a continuous depressurization system that reduces the pressure of the solids stream to a desired level for transport.

In another exemplary embodiment of the invention, a cooling system for cooling solid particles entering the cooling system at an average temperature above about 1500 ° F comprises: a cooler having an inlet for receiving solid particles at an average temperature above about 1500 ° F; the cooler has an outlet for exiting at least a portion of the average temperature of the solid particles below about 600 ° F; a heat transfer system in the cooler; and fluidized bed refluxing cooled material (cooler solid particles approaching exit temperature) in a cooler, wherein the solid particles above about 1500 ° F enter the cooler through the inlet, wherein at least a portion of the solid particles are mixed with at least a portion of the fluidized bed refluxing cooled material in the cooler until the average temperature of at least a portion of the solid particles is cooled to less than about 1000 ° F, wherein at least a portion of the solid particles below about 1000 ° F average temperature are in contact with a heat transfer system in the cooler that further cools at least a portion of the solid particles to an average temperature of less than about 600 ° F, and wherein at least a portion of the average temperature of the solid particles below about 600 ° F exits through the outlet.

The solid particles may enter the cooler through an inlet at the bottom of the cooler at an average pressure of about 30psia or greater. The solid particles may have a mass mean diameter in the range of about 50 microns to 400 microns.

The cooler may be a vertical vessel having a bottom and a top, and the inlet of the cooler may be located at the bottom of the cooler.

The cooling system may further include: a downcomer that directs solid particles at an average temperature above about 1500 ° F to the bottom of the cooler, a support near the top of the cooler in the low temperature section for supporting the heat transfer system, a second cooler, and a gas-solid particles separation system, wherein at least a portion of the average temperature of the solid particles below about 600 ° F exits the cooler through the outlet and enters the gas-solid particles separation system and then reenters the second cooler to further cool the solid particles.

The downcomer and primary solids cooler may be lined with refractory material.

The cooling system may further include: a vent filter section at the top of the second cooler to restrict entrained particulates from entering these vent lines, and a pressure control system to regulate the pressure differential between the cooler and the gasifier.

The cooling system may further comprise a continuous pressure letdown system wherein the cooled solids are withdrawn from the second cooler through a connected pressure letdown system that reduces the pressure of the solids stream to a desired pressure for transport from the second cooler.

The bottom of the primary cooler may be tapered to provide a tapered section and incorporate the inlet, and the downcomer may provide the solid particles to the inlet in the bottom of the cooler. The conical region and volume of the primary solids cooler below the heat transfer system may be sized so that there is sufficient time for the returning cold solids to mix with the entering hot solids from the downcomer.

The cooling system may further include a pressure control system to regulate a pressure differential between the cooler and the gasifier.

In another exemplary embodiment of the invention, a cooling method for cooling solid particles above an average temperature of about 1500 ° F to an average temperature of less than about 600 ° F comprises: providing solid particles having an average temperature of greater than 1500 ° F, mixing the solid particles with a fluidized bed of refluxing chilled material to form a portion of the solid particles having an average temperature of less than about 1000 ° F, and contacting the portion of the solid particles having an average temperature of less than about 1000 ° F with a heat transfer system to form a portion of the solid particles having an average temperature of less than about 600 ° F.

Such cooling methods may further include providing the solid particles at an average temperature above about 1500 ° F and an average pressure above about 30 psia.

The cooling method may further include providing solid particles having an average temperature above about 1500 ° F and a mass average diameter in a range from about 50 microns to 400 microns.

The cooling method can further include providing a primary cooler in which the cooling steps occur, supporting a heat transfer system near the top of the cooler, providing a secondary cooler, wherein at least a portion of the average temperature of the solid particles below about 600 ° F exits the primary cooler, separating the gas and solid particles before they enter the secondary cooler, and further cooling the solid particles in the secondary cooler.

The cooling method may further include: filtration is performed to restrict fine solids particles above a predetermined size from entering the vent line and to control the pressure differential between the primary cooler and the gasifier operating at an average temperature above about 1500 ° F.

The cooling method may further comprise continuously reducing the pressure of the cooled solids withdrawn from the secondary cooler to reduce the solids stream pressure to a desired level for transport from the secondary cooler.

The cooling process may further include withdrawing, cooling, and depressurizing excess solids from the gasifier at an average temperature of about 1500 ° F or greater to facilitate their disposal.

The cooling method may further comprise adjusting the rate of blowing of the solid particles in the downcomer to control the flow of solid particles caused by the hydrostatic head created by the difference in elevation.

The cooling method may further include regulating a pressure differential between the gasifier and the cooler by a vent pressure controller to further control the flow of hot solid particles to the cooler inlet.

These and other objects, features and advantages of the present invention will become more apparent upon reading the following specification in conjunction with the accompanying drawing figures.

Brief description of the drawings

The various features and advantages of this invention may be more readily understood by referring to the following detailed description in conjunction with the accompanying drawings in which like reference numerals designate like structural elements, and in which:

FIG. 1 illustrates a solids heat exchanger for processing hot solids from a high temperature, high pressure source according to an exemplary embodiment of the present invention.

FIG. 2 illustrates a bottom conical section of a primary solids cooler according to an exemplary embodiment of the present invention.

Fig. 3 illustrates a clamp arrangement for a bayonet heat exchanger tube according to an exemplary embodiment of the present invention.

Detailed description of the invention

In order to facilitate an understanding of the principles and features of various embodiments of the present invention, various illustrative embodiments are explained below. While various exemplary embodiments of the invention have been described in detail, it should be understood that other embodiments are contemplated. Thus, the scope of the present invention is not intended to be limited to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, in describing these exemplary embodiments, specific terminology will be resorted to for the sake of brevity.

It must also be noted that, unless the context clearly dictates otherwise, as used in the specification and the appended claims, the singular forms "a," "an," and "the" include plural reference. For example, reference to a component is also intended to include a combination of components. References to a composition containing "a" ingredient are intended to include other compositions in addition to the named one.

Also, in describing these exemplary embodiments, terminology will be resorted to for the sake of brevity. It is intended that each term is to be taken in its broadest sense as understood by one of ordinary skill in the art and includes all technical equivalents which operate in a similar manner to accomplish a similar purpose.

Ranges may be expressed herein as from "about" or "substantially" one particular value and/or to "about" or "substantially" another particular value. When such a range is expressed, other exemplary embodiments include from the one particular value and/or to the other particular value.

Similarly, as used herein, "substantially free of" something, or "substantially pure," and similar feature descriptions may include: is "at least substantially free of" something or "at least substantially pure", and is both "completely free of" something or "completely pure".

"comprising" or "comprises" or "comprising" means that at least the named composition, element, article, or method step is present in the composition, article, or method, but does not exclude the presence of other compositions, materials, articles, or method steps, even if such other compositions, materials, articles, or method steps perform the same function as the named.

It should also be understood that reference to one or more method steps does not preclude the presence of additional method steps or method steps intermediate to those expressly identified. Similarly, it will also be understood that reference to one or more ingredients in a composition does not preclude the presence of additional ingredients other than those explicitly identified.

These materials as described in the fabrication of the various elements of the present invention are intended to be illustrative and not limiting. Many suitable materials that will perform the same or similar function as those described herein are intended to be included within the scope of the present invention. For example, other such materials not described herein may include, but are not limited to, materials developed after the time the invention was developed.

The present invention has broad application for cooling and treating hot solid particles such as catalysts and products from different chemical reactors, as well as ash and spent sorbent particles from combustors and unutilized char mixtures from gasifiers. The detailed description of the invention is provided for a specific example of cooling and then depressurizing hot solids from a pressurized gasifier, but is equally applicable to other situations where cooling of solids from high temperature and high pressure environments is required.

As illustrated in fig. 1, solid particles produced in a reactor, combustor or gasifier 100 (the term "solid particles" is used herein to generally describe distributed particles having a mass mean diameter in the range of 50 to 400 microns, typically solid particles from a coal gasifier comprising primarily ash with little char) are withdrawn through a nozzle 110 through a connected downcomer pipe 200. The connected downcomer piping and primary cooler vessel are lined with refractory material to protect them from corrosive and high pressure environments. The operating temperature of a fluidized bed gasifier is typically in the range of about 1700 ° F to 2000 ° F and the operating pressure is in the range of about 30 to 1000 psia. In a preferred embodiment, the solid particle flow direction is generally downward at the nozzle 110. To facilitate equipment layout and plumbing connections, the nozzles may be angled between about 10 and 90 degrees from horizontal with generally downward directed flow. The plurality of blowing nozzles 250 are added if the length of the pipe is more than 20 times the diameter of the pipe. The blowing gas flow may be adjusted to flow with the hot solids to the solids cooler.

As illustrated in fig. 1, solid particles from the gasifier enter the primary cooler 300 at the bottom central opening 260. In one embodiment, the conduit 200 connecting the primary cooler 300 may have an extension 210 into the primary cooler space 300. The tapered section 320 of the refractory lined primary cooler vessel 300 and the extension of the inlet 210 form an annular cavity 310 that is a substantially stagnant zone with minimal blow-through. The purpose of this stagnant zone is to adequately collect large pieces of extraneous and foreign material entering the primary cooler and to allow safe discharge of this material from the cooler (through discharge nozzle 330) so as to limit or prevent them from interfering with the cooling operation of the solid particles. The extension of the pipe and the no-flow band are not necessary for the application of solid particles entering the cooler to be free of extraneous material.

With minimal air blowing, the annular cavity 310 may be fluidized to separate extraneous materials from the standard ash particles. One advantage of this configuration is that the cross-sectional area of the annular cavity 310 can be designed as desired by adjusting the size, shape and angle of the elongated central conduit and the cone, thereby minimizing the consumption of blowing gas to fluidize the small particles and separate the larger particles from the smaller particles. One of ordinary skill in the art can devise different ways of separating extraneous materials from a normally operating mixture of solid particles, such as ash and char from a gasifier, based on size separation.

FIG. 2 shows an example of a design of a tapered section and an elongated central tube for separating extraneous material from a standard ash mixture. The central tube 210 may have another tapered section 215, the angle of which may be adjusted to achieve a desired cross-sectional area between the vessel and the taper 215 to minimize the need for fluidization gas. Blowing gas 335 is applied to different nozzles around the cone. The blowing gas fluidizes the solid particles in the upper section of the primary cooler for better heat transfer. Extraneous material, typically large pieces of crushed refractory and slag lumps, sink to the bottom of the primary cooler and are discharged through a discharge pipe 330. According to this process, the annular cavity space 340 formed between the central tube 215 and the container cone 360 can be used to store extraneous material during normal operation and be removed at the end of this process.

Referring to the embodiment in FIG. 2, after the large pieces of extraneous material have been separated from the standard ash, the hot ash stream 260 entering the primary cooler is mixed with an internally circulating cooler ash stream 345 having a temperature in the range of about 400F to 600F. The mixture temperature of the solid particles is in the range of about 800 ° F to 1000 ° F due to the mixing of the two streams. Thus, the temperature of the cooling surface (e.g., the outer pipe 400 of the bayonet tube arrangement in fig. 1) in contact with the fluidized solid particles is well below the temperature of about 1500 ° F to 2200 ° F from the inlet of the gasifier. Cryogenic solid particles of about 800 ° F to 1000 ° F in contact with ash cooling surfaces minimize, if not eliminate, the need for expensive alloy materials as the material used to construct the cooling surface. The entire cooling surface in the primary cooler in the first stage can be constructed by using ordinary carbon steel.

The solid particle mixture flows upwards in the primary cooler due to gas drag and due to the pressure difference between the cooled solid particle inlet 260 and the solid particle outlet 370. The gas-solid particle mixture contacts the cooling surface 400 in the primary cooler. In the preferred embodiment, this cooling surface is made of bayonet-type cooling ducts, which comprise two concentric tubes: such as outer tube 400 and inner tube 410 shown in fig. 1.

The coolant fluid (water) flows preferably downward under gravity from the steam drum 500 into the space 420 formed by the vessel wall 380 and tube sheet 430 of the primary cooler. The water is distributed into a plurality of tubes (inner tubes 410) attached to a tube sheet 430. As illustrated in fig. 3, water flows downward in the inner tube 410, forming a water-steam mixture as it absorbs heat, and then two-phase steam bubbles and saturated water flow upward in the annular space formed by the inner tube 410 and the outer tube 400. The heat source for evaporating a portion of the water in the annular space into steam bubbles is a fluidized bed of hot ash having a temperature of about 800 ° F to 1000 ° F surrounding the outer tube. The steam bubbles are separated from the water in the steam drum and the steam is vented through a drum pressure control valve, typically maintaining the steam drum pressure at about 50 psi.

The size of the primary solids cooler and the extent of the heat transfer area required depends on the desired exit temperature of the solids. From both a performance and economic standpoint, it is desirable to cool the ash to a primary cooler exit temperature of about 400 ° F to 600 ° F. Allowing the cooler water to flow through the cooling tube bundle 900 may accomplish further cooling of the cooler in the secondary cooler 700 (fig. 1).

As illustrated in FIG. 1, ash cooled to about 400F to 600F overflows from near the top of the primary solids cooler through outlet 370. The fluidizing gas also exits the primary cooler with these solid particles and flows through conduit 600 into gas-solid particle separation system 800 embedded in secondary cooler 700. The gas-solid particle separation system generally includes a cyclone having a dipleg and a seal (e.g., ring seal 800) for the dipleg. The purpose of the gas-solids separator is to prevent the gas from carrying a significant amount of solids to the baffle filter 710. After a substantial portion of these solid particles are separated from the gas-solid particle stream flowing into the cyclone, the fine particle entrained gas exiting the cyclone flows upward through the distribution conduit 810.

The distributor at the outlet 810 distributes the gas evenly to the barrier filters 710. These barrier filters are typically made of a plurality of sintered metal filters to block fine particles and allow cleaner gas to permeate through the filters. The filtered gas flows through the pressure control valve 750 and is discharged to a suitable location, preferably downstream of the process stream at lower pressure. The fluidizing gas from the primary solids cooler is thus cleaned and discharged not back to the gasifier but to downstream processing. In this way, the amount of fluidizing gas in the primary cooler can be optimized to achieve the desired internal solids circulation and maximize heat transfer from the fluidized bed.

The released solids from the secondary cooler cyclones and the ring seal 800 are cooled to the desired exit temperature by flowing through a set of cooling surfaces 900 along with the fine solids from the baffle filters 710. The blow-off gas 335 from the secondary cooler is also filtered and vented through a pressure control valve 750. The cooled solid particles are then discharged through exit nozzle 950 at the bottom of the secondary cooler. The cooled solid particles leaving 950 are still at the high gasifier operating pressure. It is preferred that the ash be depressurized through a continuous ash depressurization system such as that disclosed in U.S. patent publication No. 2010/0266460, the teachings of which are incorporated herein by reference. 2010/0266460 discloses a continuous pressure reduction system having pressure reduction devices that facilitate pressure reduction of a stream of solid particles from a high operating system pressure to a lower pressure required for downstream processing.

FIG. 3 provides a method of limiting or preventing vibration of the inner tube 410 of the bayonet tube arrangement. An omega clip 440 is welded to the inner tube 410 on one leg of the omega clip. The top of the omega-shaped member is in contact with the outer tube 400. The omega clamps are typically positioned at three foot intervals and at 120 degree orientations. With this embodiment, the inner tube is constrained by an Ω clamp. One skilled in the art can devise several methods for suppressing the effects of external pipe vibrations while allowing axial expansion. It is critical that the confinement mechanism be supported from the upper section of the primary cooler, which is typically below 600 ° F, for example, depending on the length of the tubes, and one or more confinement grids.

Water flowing through the inner tube 410 from the drum exits the inner tube through the defined section 450 at a velocity in the range of about 5 to 15 ft/s. This speed limit either prevents dirt from accumulating in the water system or from adhering to low points in the bayonet tube. The lower portion of the outer conduit is clad with a thick metal cap 460 to limit or prevent corrosion.

During operation of the gasifier, coal ash accumulates in the gasifier. The circulating solids inventory in the gasifier is maintained by removing accumulated coal ash through a solids cooler system. The high temperature ash is cooled and depressurized for transport to an ash drum for disposal. As illustrated in fig. 1, the solid particle transfer nozzle 110 on the gasifier is located approximately five feet above the primary cooler overflow outlet nozzle 370. This arrangement creates a hydrostatic head for the solids to naturally flow from the gasifier to the primary solids cooler to be fluidized whenever the connected J-downcomer conduit is fluidized. In addition to hydrostatic head, the flow of solids is controlled by a discharge control valve 750. In operation, the pressure differential between the take-off point and the discharge pressure caused by 750 is used for coarse control and the flow of fluidizing gas in the connected J-downcomer piping is used for fine control of the hot solids to the primary solids cooler.

Numerous characteristics and advantages have been set forth in the foregoing description, together with details of the structure and function. While the invention has been disclosed in several forms, it will be apparent to those skilled in the art that many modifications, additions, and deletions can be made, particularly in relation to the shape, size, and arrangement of parts, without departing from the spirit and scope of the invention and its equivalents as set forth in the following claims. Accordingly, other changes or embodiments may be suggested by the teachings herein, which fall within the breadth and scope of the claims appended hereto, and may be particularly reserved.

Claims (26)

1. A cooling system for cooling solid particles having an average temperature of greater than 1500 ° F entering the cooling system, the cooling system comprising:

a cooler having an inlet at a bottom for receiving solid particles at an average temperature above 1500 ° F, the cooler having an outlet in an upper section for exiting at least a portion of the solid particles at an average temperature below 600 ° F;

a heat transfer system in the cooler; and

the fluidized bed in the cooler refluxes the cooled material;

wherein the solid particles enter the cooler through the inlet at an average temperature above 1500 ° F;

wherein at least a portion of the solid particles are mixed with at least a portion of the fluidized bed refluxing cooling material in the lower section of the cooler until the average temperature of at least a portion of the solid particles is cooled to less than 1000 ° F;

wherein at least a portion of the solid particles having an average temperature of less than 1000 ° F contact a heat transfer system in the cooler that further cools at least a portion of the solid particles to an average temperature of less than 600 ° F; and is

Wherein at least a portion of the solid particles having an average temperature of less than 600 ° F exit the cooler through the outlet.

2. The cooling system of claim 1, wherein the solid particles enter the cooler through the inlet at an average pressure above 30 pisa.

3. The cooling system of claim 1, wherein the solid particles have a mass mean diameter in a range of 50 microns to 400 microns.

4. The cooling system of claim 1, further comprising:

a downcomer that introduces the solid particles at an average temperature above 1500 ° F to the cooler bottom;

a support proximate the top of the cooler for supporting the heat transfer system;

a second cooler; and a gas-solid particle separation system;

wherein at least a portion of the average temperature of the solid particles below 600 ° F exits the cooler through the outlet and enters the gas-solid particle separation system and then the second cooler to further cool the solid particles.

5. The cooling system of claim 4, further comprising:

a vent filter section at the top of the second cooler for restricting solid particles above a predetermined size from entering the vent line; and

a pressure control system for regulating a pressure differential between the cooler and a gasifier connected to the downcomer.

6. The cooling system of claim 5, further comprising a continuous pressure reduction system, wherein the cooled solid particles are withdrawn from the second cooler through the continuous pressure reduction system, the continuous pressure reduction system reducing the pressure of the solid particle stream to a desired level for transport from the second cooler.

7. The cooling system according to claim 1, wherein the solid particles enter the cooler through the inlet at an average temperature between 1500 ° F and 2200 ° F;

wherein the solid particles enter the cooler through the inlet at an average pressure between 30psia and 1000 psia; and is

Wherein the solid particles have a mass mean diameter between 50 and 400 microns.

8. The cooling system according to claim 7, further comprising a downcomer, wherein the cooler is a vertical vessel, wherein the cooler bottom is conical and merges into the inlet, and wherein the downcomer provides the solid particles to the inlet in the cooler bottom.

9. The cooling system of claim 7, further comprising:

a second cooler; and

a gas-solid particle separation system;

wherein at least a portion of the average temperature of the solid particles below 600 ° F exits the cooler through the outlet and enters the gas-solid particle separation system and then enters the second cooler to further cool the solid particles.

10. The cooling system of claim 7, further comprising a pressure control system for regulating a pressure differential between the cooler and a gasifier connected to the cooler.

11. A system for cooling ash and solid particles from a high temperature and high pressure coal gasification environment, the cooling system comprising:

a gasifier;

a primary solids cooler;

a downcomer connecting the gasifier and the primary solids cooler and introducing the solids to the bottom of the primary solids cooler;

a heat transfer system in the primary solids cooler for exchanging heat between the solids and a cooling medium;

a support near the top of the cooler for supporting the heat transfer system;

a solids outlet near the top of the primary solids cooler;

a secondary cooler;

a gas-solid particle separation system at the inlet of the secondary cooler;

a vent filter section near the top of the secondary cooler for restricting solid particles above a predetermined size from entering the vent line;

a pressure control vent valve for controlling a pressure differential between the primary solids cooler and the gasifier; and

a continuous pressure reduction system, wherein the cooled solid particles are withdrawn from the secondary cooler through the continuous pressure reduction system, which reduces the pressure of the stream of solid particles to a desired level for transport from the secondary cooler.

12. The system of claim 11, wherein the system cools and depressurizes ash or solid particles from a gasifier operating at an average temperature between 1500 ° F and 2200 ° F and an average pressure between 30psia and 1000 psia;

wherein the ash and solid particles have a mass mean diameter between 50 microns and 400 microns;

wherein a solids outlet near the top of the primary solids cooler provides an outlet for at least a portion of the average temperature of the solids below 600 ° F;

wherein at least a portion of the solid particles are mixed with fluidized bed refluxing cooling material in the primary solid particle cooler until the average temperature of at least a portion of the solid particles is cooled to less than 1000 ° F;

wherein at least a portion of the average temperature of the solid particles less than 1000 ° F is contacted with a heat transfer system in the primary solid particle cooler that further cools at least a portion of the solid particles to an average temperature of less than 600 ° F; and is

Wherein at least a portion of the average temperature of the solids below 600 ° F exits the primary solids cooler through a solids outlet.

13. The system of claim 11, wherein the secondary cooler comprises a non-refractory lined vessel.

14. The system of claim 11, wherein the bottom of the primary solids cooler is tapered to provide a tapered region, and wherein the tapered region and volume of the primary solids cooler below the heat transfer system are sized so that the returning cold solids have sufficient time to mix with the entering solids from the downcomer.

15. The system of claim 11, wherein the heat transfer system comprises bayonet-type cooling tubes.

16. A system according to claim 15, further comprising omega springs attached to the bayonet cooling tubes to reduce vibration.

17. The system of claim 11, wherein the solids exit the gasifier at a location higher than a solids exit near a top of the primary solids cooler.

18. A method of cooling solids above an average temperature of 1500 ° F to an average temperature of less than 600 ° F based on the cooling system of claim 1.

19. The method of cooling according to claim 18, further comprising providing the solid particles at an average temperature of greater than 1500 ° F, an average pressure of greater than 30 psia.

20. The method of cooling according to claim 18, further comprising providing the solid particles at an average temperature above 1500 ° F, a mass mean diameter in the range of 50 microns to 400 microns.

21. The method of cooling of claim 18, further comprising:

providing a primary cooler in which these cooling steps occur;

supporting the heat transfer system in a lower temperature section near the top of the cooler;

providing a secondary cooler, wherein at least a portion of the average temperature of the solid particles below 600 ° F exits the primary cooler;

separating the gas and solid particles before they enter the secondary cooler; and is

The solid particles are cooled in the secondary cooler.

22. The method of cooling of claim 21, further comprising:

filtering to restrict solid particles exceeding a predetermined size from entering the vent line; and is

The pressure differential between the gasifier providing the solid particles at an average temperature above 1500 ° F and the primary cooler is controlled.

23. The method of cooling according to claim 21 further comprising continuously reducing the pressure of the cooled solids withdrawn from the secondary cooler to reduce the pressure of the solids stream to a desired level for transport from the secondary cooler.

24. The method of cooling according to claim 22, further comprising withdrawing, cooling and depressurizing excess solid particulates from the gasifier at an average temperature of 1500 ° F or greater to facilitate their disposal.

25. The method of cooling according to claim 18, further comprising blowing the solid particles in a downcomer prior to mixing the solid particles with the fluidized bed of refluxing cooling material, and adjusting the blowing rate to control the flow of the solid particles caused by hydrostatic head resulting from height difference.

26. The method of cooling according to claim 22, further comprising adjusting a pressure differential between the gasifier and the primary cooler to control the flow of hot solid particles to the primary cooler.