CN1268902A - Method and apparatus for upgrading solid material - Google Patents

Abstract

A method and an apparatus for upgrading a solid material is disclosed. The method comprises heating the solid material to an elevated temperature to remove water and thereafter cooling the upgraded solid material. The method includes providing a plurality of vessels containing packed beds of the solid material and one or more than one heat exchange circuit for heating and cooling the solid material in the packed beds in the vessels by heat exchange with a heat transfer fluid. The method is controlled so that the solid material in a first group of the vessels is at one or more stages of a heating cycle and the solid material in a second group of vessels is at one or more stages of a cooling cycle. Specifically, the method is controlled by selectively connecting the one or more than one heat exchange circuit to the vessels so that the heat transfer fluid recovers heat from the solid material undergoing the cooling cycle in at least one of the vessels in the first group and transfers the recovered heat to the solid material undergoing the heating cycle in at least one of the vessels in the second group.

Description

Method and device for improving solid material grade

The invention relates to improving the grade of solid materials.

In particular, but not exclusively, the invention relates to upgrading solid materials having low thermal conductivity.

More particularly, this invention relates to methods for improving the grade of solid materials by removing water from the materials. The method comprises: heating the solid material to a high temperature while protecting high pressure, and then cooling the improved material to room temperature.

A particular application of the invention is to upgrade carbonaceous materials (typically coal) to increase their BTU value.

US Patent 5,290,523 to Koppelman discloses a method of simultaneously applying temperature and pressure to upgrade the grade of coal.

Koppelman discloses a process for thermal dehydration of coal: heating the coal at high temperature and pressure causes changes in its physical properties, whereby water is removed from the coal by a "squeezing" action.

Koppelman also discloses maintaining a sufficiently high pressure in the process that the by-product water produced is primarily liquid rather than steam.

Koppelman also discloses a selection of a range of different apparatus for carrying out the method.

Typically, the selection is based on heating the coal in a pressure vessel. The pressure vessel includes an inverted tapered inlet, a cylindrical vessel body, a tapered outlet and a vertically or horizontally mounted heat exchange tube assembly located in the vessel body.

In one arrangement, vertically distributed tubes and outlets are filled with coal and nitrogen is injected to prepressurize the tubes and outlets. Oil is supplied as heat exchange fluid to the outer cylinder of the tube for indirect heat exchange to heat the coal. Further heating is provided by direct heat exchange of coal and steam (used as working fluid in the packed bed). Additionally, the water vapor pressurizes the tube and outlet port to the desired pressure.

A combination of high temperature and high pressure conditions at the tube and outlet ends can evaporate some of the water from the coal, which then condenses into a liquid. Due to the high pressure, part of the water vapor generated after adding water also condenses into liquid in the cooler area. Excess water vapor that is not condensed and required for optimal precompression of the packed bed must be extracted. In addition, non-condensable gases (such as CO, CO ₂ ) are produced, which also need to be extracted. Periodically drain the liquid from the outlet.

Finally, after a predetermined residence time, the vessel is depressurized to discharge the hot, upgraded coal through the outlet port to a conveyor that transfers the coal to a wet auger. Water is sprayed onto the hot, upgraded coal while the conveyor transfers the coal to the wet auger. The coal is further cooled in the wet booster and then spread in a thin layer in the storage area to cool to room temperature.

It is an object of the present invention to provide an improved method and apparatus for upgrading coal as compared to the method described by Koppelman.

According to the first aspect of the present invention, there is provided a method for improving the grade of solid materials, the method comprising: heating the solid materials to a high temperature to remove moisture, and then cooling the materials with improved grades, characterized in that:

(i) providing a series of vessels containing packed beds of solid material and one or more heat exchange circuits capable of heating or cooling the solid material in the packed beds of vessels by heat exchange with a heat transfer fluid; and

(ii) control the method so that the solid material in the first group of containers is in one or more stages of heating cycle, while the solid material in the second group of containers is in one or more stages of cooling cycle, the control step comprises: selectively connecting one or more heat exchange circuits to the vessels so that the heat transfer fluid can recover thermal energy from the solid material undergoing a cooling cycle in a first set of at least one vessel and then transfer the recovered heat energy to a second set of at least one vessel Solid material subjected to heating cycle.

The basis of the present invention is to recover heat energy from solid material being cooled in one set of containers and then use the recovered heat energy to heat solid material in another set of containers.

In one aspect of the present invention, a set of heat exchange circuits is provided, the heat exchange circuits selectively connect the pairs of containers, so that the heat exchange fluid in each heat exchange circuit cools the solid material in one of the pairs of containers, and then , through heat exchange with the solid in each pair of containers, the solid material in the other container of each pair of containers is heated.

The heat exchange fluid in each heat exchange circuit heats or cools the solid material in each pair of containers in the heating and cooling cycle. Solid materials are heated or cooled.

For example, a heat exchange circuit heats the solid material in a container from room temperature to a temperature T1; and another heat exchange circuit is subsequently connected to the container to heat the solid material from T1 to a higher temperature T2. At the same time, the heat exchange circuit cools the solid material in another container from the highest temperature of the heating cycle to a lower temperature.

Preferably, the contents of the container are under high pressure during the heating and cooling cycles.

Solid material can be kept in a container during heating and cooling cycles.

Alternatively, solid materials can be heated in one vessel in a heating cycle, transferred while hot to another vessel, and cooled in a cooling cycle.

Preferably the heat exchange loop heats and cools the solid material via indirect heat exchange.

The method of the present invention has great flexibility, the solid material can be applied to the heating and cooling cycle, and at the same time the advantage is that the solid material in the heating cycle is heated by the heat energy recovered from the solid material in the cooling cycle.

For example, the method can be used to upgrade solid carbonaceous materials such as coal by removing water from coal in a two-step process using a combination of pressure and temperature:

(i) in the first "wet" step, water is "squeezed" from the coal and discharged in a liquid phase; and

(ii) During the first "dry" step, a significant portion of the remaining water in the coal is removed in the vapor phase.

The heat exchange fluid may be any suitable fluid that transfers energy via indirect heat exchange.

For example, the heat exchange fluid may be a fluid such as oil that is single phase within the operating temperature range of the heating and cooling cycle.

For example, the heat exchange fluid may be a fluid such as water that is in liquid and gaseous phases at the operating temperature range and appropriate pressure of the heating and cooling cycles.

The method may include one or more additional heating steps to complete the heating cycle.

The method may include one or more additional cooling steps to complete the cooling cycle.

The additional heating step may be any suitable method, such as feeding an oxygen-containing gas into the vessel for oxidative heating in the vessel.

Additional cooling steps may be by any suitable method, such as direct contact of the coal with dry or moist air in the same or another vessel.

Preferably, the method further comprises supplying a working fluid into the vessel, heating or cooling the solid material by direct heat exchange with the solid material, and pressurizing the contents of the vessel.

According to a first aspect of the present invention, there is provided a device for improving the grade of solid materials, which includes:

(a) a series of vessels containing packed beds of solid material at high temperature and pressure;

(b) one or more heat exchange circuits capable of heating or cooling the solid material in the packed bed of the vessel by heat exchange with a heat transfer fluid;

(c) Means for connecting the or each heat exchange circuit to the vessels so that the solid material used in one set of vessels is heated by the heat exchange fluid according to a predetermined heating cycle and the solid material in the other set of vessels is heated according to a predetermined heating cycle. The cooling circuit is cooled by heat exchange fluid, wherein in use, the or each heat exchange circuit is connected to the container, so that each heat exchange circuit removes heat from the solid material of at least one container and transfers the recovered heat to at least solid material in one other container; and

(d) selectively modifying the means of connection between the heat exchange circuit and the vessel to heat and cool the solid material in the vessel in accordance with the heating and cooling cycles.

The heat exchange loop may be of any suitable configuration.

Preferably the heat exchange circuit comprises: (i) a heat exchange assembly located in the vessel; and (ii) means for circulating a heat exchange fluid through the heat exchange assembly of the vessel and between the assemblies.

It is particularly preferred that the heat exchange assembly of each vessel comprises:

(i) a heat exchange plate assembly having one or more passages for a heat exchange fluid located in a container;

(ii) supplying heat exchange fluid to the inlet of the channel; and

(iii) Outlets for expelling heat exchange fluid from the channels.

Preferably the plate has minimal heat capacity.

Preferably the means for selectively varying the connection between the heat exchange circuit and the vessel comprises suitable control means.

According to a second aspect of the present invention, a method for improving the grade of solid materials is provided, comprising:

(i) adding solid material to the container to form a packed bed of solid material;

(ii) heating and pressurizing the solid material to remove moisture, the heating step comprising heating the solid material through indirect heat exchange with a heat exchange fluid;

(iii) cooling the solid material under high pressure; and

(iv) Discharging the cooled upgraded solids material.

The basis of the above aspects of the invention is the multifunctional container which accommodates the charge of solid material which is then held in a packed bed for heating and cooling cycles.

A great advantage of the above described method and apparatus of the present invention is that the use of multifunctional containers minimizes the handling of hot solids material compared to what Koppelman required.

Another benefit is that the multi-function container minimizes the cycle time associated with emptying, filling, pressurizing and depressurizing compared to Koppelman's need.

Preferably, the heating step also includes heating the solid material with the working fluid through direct heat exchange.

The first aspect of the energy recovery of the present invention can be carried out with or without the multifunctional container of the second aspect of the present invention.

Similarly, the multi-purpose container of the second aspect of the invention may be used with or without the energy recovery of the first aspect of the invention.

In one version of the first aspect of the invention, the five vessels A, B, C, D, E comprise high pressure packed beds, and each vessel is in a different heating and cooling cycle stage to remove water from the coal, increasing the coal's grade. The heating cycle of the method includes:

(i) transferring heat to the coal so that the water in the coal is removed as a liquid phase in the first "wet" stage of the process; and

(ii) transferring heat to the coal, boiling at least a portion of the remaining water in the coal as a vapor phase in the second "dry" stage of the process, and then heating the coal to final product temperature.

Coal heated in each packed bed is subjected to indirect heat exchange through a heat exchange fluid pumped through a heat exchange circuit sequentially connected to each pair of containers. The heat exchange circuit for each pair of vessels includes heat exchange plates having one or more passages for heat exchange fluid in each vessel and means for circulating the heat exchange fluid through the heat exchange modules of each pair of vessels. The arrangement of a pair of vessels and a heat exchange circuit is shown in Figure 1. In this figure, vessel 3a contains a packed bed of coal in a heating cycle; and vessel 3b contains a packed bed of coal in a cooling cycle. The heat exchange plate number in the container is 5. The heat transfer cycle set includes lines and pumps, numbered 7 and 9, respectively.

The vessel and heat exchange circuit may be any suitable pressure vessel, as described in the Applicant's applications: PCT/AU98/00005 (entitled "Reactor"), PCT/AU98/00142 (entitled "Process Feed Process Vessel and Method"), PCT/AU98/00204 (entitled "Liquid/Gas/Solid Separation") and PCT/AU98/00324 (entitled "Improved Heat Exchange") and Australian provisional application PO8767. The disclosures of these patent applications are incorporated herein by reference.

The heating or cooling of the coal in the vessel can be further facilitated by supplying the working fluid to the packed bed in the vessel. Working fluid:

(i) heating or cooling the coal by direct heat exchange between the coal and the working fluid and between the working fluid and the heat transfer fluid in the heat exchange circuit; and

(ii) Pressurize the container contents.

The working fluid circulation circuit is shown in number 11 in FIG. 1 .

The connection of the heat exchange circuit to the vessel is selected so that the heat transfer fluid can recover heat energy from a vessel containing a solid material undergoing a cooling cycle and transfer the recovered heat energy to another vessel containing a solid material undergoing a heating cycle.

Figure 2 shows the connection of a single heat exchange circuit to a series of paired vessels A, B, C, D, E. This is a single stage energy recovery cycle.

Figure 2 shows that when vessel A contains a packed bed of coal at the final desired product temperature of 371°C and vessel D contains a packed bed of coal at room temperature of 25°C, the connection of the heat exchange circuit to vessels A and D gives the following results:

(i) cooling the coal in vessel A from 371°C to 230°C; and

(ii) The coal in vessel D is heated from 25°C to 185°C by indirect heat exchange using the heat recovered from vessel A.

The heat transfer connection of the packed beds of vessels A and B as described above results in a packed bed close to its "common approximate temperature" (determined by relative heat capacity and heat loss).

Figure 2 also shows that additional cooling and heating treatments are then provided to vessels A and D, respectively, to obtain:

(i) further cooling the coal in container A from 230°C to room temperature; and

(ii) Further heating the coal in vessel A to its final desired product temperature of 371°C.

Additional heating and cooling is performed using condensers and boilers or other suitable equipment.

As can be understood from the above discussion and Figure 2, the heat exchange circuits for heating and cooling the coal in vessels A and D are selectively combined with the other pairs of vessels A, B, C, D, E according to the table shown in Figure 2 Similar coal heating and cooling can be obtained in these vessels by making connections sequentially and optionally providing external heating and cooling to vessels as in vessels A and D.

Various changes can be made to the above method and apparatus for improving the grade of solid materials without departing from the spirit and scope of the present invention.

For example, the first aspect of the invention is not limited to the single stage energy recovery cycle with 5 reactors as depicted in FIG. 1 . For example, the first aspect can also be extended to a 2-stage energy recovery cycle with additional heating and cooling in 3 vessels. With this design, the heating and cooling steps are arranged countercurrently in time and with two approximate temperatures, typically 240°C and 150°C. More specifically, the two-stage energy recovery cycle works as follows: The hot vessel A that has just completed the heating cycle is connected to the cooler vessel B to transfer heat to heat vessel B in the second stage of heating. If the two approximate temperatures reach the higher temperature, container A is connected to a cold container C to transfer heat so that container C is heated in the first stage of heating. Finally, if a lower approximate temperature is reached, vessel A is connected to a condenser to complete the cooling of the coal in this vessel, resulting in a cold final product. Vessel B, which has been heated to a higher approximate temperature in the second heat treatment, is connected to a water vapor supply circuit to complete the heating cycle in this vessel. It will be appreciated that the sequence of heating and cooling of the newly filled coal bed vessel may be repeated.

Claims (15)

1. A method for improving the grade of solid materials, the method comprising: heating the solid materials to a high temperature to remove moisture, then cooling the materials with improved grades, characterized in that: (i) providing a series of vessels containing packed beds of solid material and one or more heat exchange circuits capable of heating or cooling the solid material in the packed beds of vessels by heat exchange with a heat transfer fluid; and (ii) control the method so that the solid material in the first group of containers is in one or more stages of heating cycle, while the solid material in the second group of containers is in one or more stages of cooling cycle, the control step comprises: selectively connecting one or more heat exchange circuits to the vessels so that the heat transfer fluid can recover thermal energy from the solid material undergoing a cooling cycle in a first set of at least one vessel and then transfer the recovered heat energy to a second set of at least one vessel Solid material subjected to heating cycle. 2. The method of claim 1, wherein step (ii) comprises selectively connecting pairs of vessels so that the heat exchange fluid in one or more heat exchange circuits cools the solid material in one of each pair of vessels, and then, The solid material in the other vessel of each pair of vessels is heated by exchanging heat with the solids in the vessel pair. 3. The method of claim 2, wherein the heat exchange fluid in one or more heat exchange circuits heats and cools the solid material in each pair of containers to different temperatures in the heating and cooling cycle, and the result is: through a series of In the step of connecting one or more heat exchange circuits to the containers in sequence, the solid materials in each container can be heated or cooled. 4. The method of claim 3, wherein a heat exchange circuit is used to heat the solid material in a container from room temperature to temperature T ₁ ; and another heat exchange circuit is connected to the container subsequently to heat the solid material from T ₁ to a higher temperature. The temperature T ₂ . 5. The method of any one of the preceding claims, wherein the contents of the vessel are under high pressure during the heating and cooling cycle. 6. A method as claimed in any one of the preceding claims, wherein the solid material is held in a vessel during the heating and cooling cycles. 7. The method of any one of claims 1-5, comprising: heating the solid material in a vessel in a heating cycle, then transferring the heated solid material to another vessel, and then cooling it in the other vessel according to the cooling cycle Allow to cool. 8. The process of any one of the preceding claims, wherein one or more heat exchange circuits heat and cool the solid material by direct heat exchange. 9. The process of any one of claims 1-7, wherein the one or more heat exchange circuits heat and cool the solid material by indirect heat exchange. 10. The method of claim 9, further comprising supplying a working fluid to the vessel to heat and cool the solid material by direct heat exchange with the solid material and pressurizing the vessel contents. 11. A device for improving the grade of solid materials, comprising: (a) a series of vessels containing packed beds of high temperature and high pressure solid material; (b) one or more heat exchange circuits capable of heating and cooling the solid material in the packed bed of the vessel by heat exchange with a heat transfer fluid; (c) Means for connecting one or more heat exchange circuits to the vessels so that the solid material used in one set of vessels is heated by the heat exchange fluid according to a predetermined heating cycle, while the solid material in another set of vessels is heated according to the A predetermined cooling circuit is cooled by a heat exchange fluid, wherein in use one or more heat exchange circuits are connected to the vessel so that each heat exchange circuit removes heat from the solid material of at least one vessel and transfers the recovered heat to solid material in at least one other container; and (d) selectively modifying one or more heat exchange circuits and means of connection between the vessel to heat and cool the solid material in the vessel in accordance with the heating and cooling cycles. 12. The apparatus of claim 11, wherein the heat exchange circuit comprises: (i) heat exchange components located in each container; and (ii) circulation of heat exchange fluid through the heat exchange components of the vessel and means between the components. 13. The apparatus of claim 12, wherein the heat exchange assembly of each vessel comprises: (i) a heat exchange plate assembly having one or more passages for a heat exchange fluid located in a container; (ii) supplying heat exchange fluid to the inlet of the channel; and (iii) Outlets for expelling heat exchange fluid from the channels. 14. A method for improving the grade of solid materials, comprising: (i) adding solid material to the container to form a packed bed of solid material; (ii) heating and pressurizing the solid material to remove moisture, the heating step comprising heating the solid material through indirect heat exchange with a heat exchange fluid; (iii) cooling the solid material under high pressure; and (iv) Discharging the cooled upgraded solids material. 15. The method of claim 14, wherein the heating step further comprises heating the solid material by direct heat exchange with the working fluid.

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