JPH048478B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for recovering thermal energy from high-temperature ash slurry produced by washing gas generated during partial oxidation or normal combustion of coal or hydrocarbons with water. It is. [Background of the Invention] Water gas containing hydrogen and carbon monoxide used in ammonia synthesis or methanol synthesis is usually crude oil, heavy oil, residual oil, petroleum pit,
It is produced by partially oxidizing (gasifying) hydrocarbons such as naphtha and petroleum coke, or coal, using an oxygen-containing gas such as pure oxygen or air under conditions of normal pressure to 100 atmospheres. This water gas is a high-temperature gas of 500 to 1500°C, and contains unburned carbon generated during partial oxidation and ash contained in the raw materials as solid substances. It is therefore necessary to remove such solids from the water gas. For this reason, after the water gas is generated, it is once washed with water before being used later. Solid matter such as unburned carbon and ash contained in the water gas is transferred to the water used for this cleaning, forming a slurry (usually called ash slurry). Since the water gas is at a high temperature, the ash slurry produced by cleaning it also has a temperature of 100 to 300 degrees Celsius.
The temperature and pressure become high. For this reason,
Ash slurry is introduced into a heat exchanger, and the heat exchanger is used to recover thermal energy contained in the Ash slurry using a cooling medium such as water. However, in addition to the solid matter present in the high-temperature ash slurry as mentioned above, a part of the ash content such as metals and heavy metals forms various compounds and dissolves. When a type heat exchanger is used, the above-mentioned compounds may precipitate inside the heat exchanger. Additionally, solids contained in the slurry may adhere to the inside of the tube. The compounds precipitated and the solid matter adhering to the inside of the tubes in this way become a factor that causes a decrease in the heat exchange efficiency of the heat exchanger. Furthermore, there is the problem that the heat exchanger may eventually become clogged with the precipitated compounds and solids mentioned above. This tendency becomes more pronounced as the quality of the raw material hydrocarbons or coal becomes lower. In particular, when heat is recovered from high-temperature ash slurry produced by washing water gas obtained by partially oxidizing coal, clogging of the heat exchanger is likely to occur. These problems are not limited to partial oxidation, but also occur when cooling the high-temperature ash slurry produced by washing the combustion gas generated from the normal combustion of coal or hydrocarbons in boilers, etc. It is also a problem that arises. [Objective of the Invention] The present invention provides a high-temperature assembly that reduces the occurrence of troubles such as blockage of heat exchange means or reduction in heat exchange efficiency, and can effectively and stably recover heat over a long period of time. The purpose of this project is to provide a method for recovering heat from Eusuraly. [Summary of the Invention] The present invention provides high-temperature ash slurry with a temperature of 100°C or higher produced by washing with water gas containing solids such as unburned carbon and ash obtained by oxidizing coal or hydrocarbons. , at least a part of the water contained in the slurry is evaporated by introducing it into a flashing device and flashing it, and the generated water vapor is introduced into a heat exchange means, and the water vapor is mixed with the cooling liquid introduced into the heat exchange means. The heat possessed by the water vapor is recovered by heat exchange, and the remaining ash slurry flashed in the flashing device is discharged from the flashing device and introduced into the next flashing device to be flushed. The water vapor generated by evaporating at least a portion of the water remaining in the water vapor is introduced into a heat exchange means, and the heat possessed by the water vapor is further recovered by heat exchange with the cooling liquid introduced into the heat exchange means. The main feature lies in the method of recovering heat from the slurry. [Effects of the Invention] The method of recovering heat from high-temperature ash slurry of the present invention does not directly introduce the high-temperature ash slurry into the heat exchange means, but instead introduces the high-temperature ash slurry into the flashing device once, and then removes the heat from the ash slurry. Since the water vapor generated by flashing in the device is introduced into the heat exchanger, solids and compounds contained in the high-temperature ash slurry (dissolved impurities) are not introduced into the tubes of the heat exchange means. do not have. Therefore, there is no problem such as a decrease in heat exchange efficiency or blockage of the heat exchanger due to precipitation or adhesion of solids or the above-mentioned compounds, and heat can be efficiently transferred from high-temperature ash slurry over a long period of time. It can be recovered. By adopting such a method, no decrease in heat recovery efficiency is observed. [Detailed Description of the Invention] Basically, the present invention does not directly introduce high-temperature ash slurry into heat exchange means, but flashes the slurry to evaporate water contained in the slurry and generate high-temperature steam. Then, this high-temperature steam is introduced into a heat exchange means to perform heat exchange and recover the heat, and the flashing of such high-temperature ash slurry and the heat exchange from the high-temperature steam generated by the flashing are utilized. It is characterized by performing the heat recovery operation in at least two stages. The high-temperature ash slurry from which heat is recovered in the heat recovery method of the present invention is gas generated during combustion of coal or hydrocarbons, or during partial oxidation thereof. Specific examples of such gas include hydrocarbons such as crude oil, heavy oil, residual oil, petroleum pitch and petroleum coke, water gas produced by partial oxidation of coal, and the above-mentioned hydrocarbons or Examples include combustion gas generated when coal is burned in a boiler. Examples of the above partial oxidation include the Texaco method. In particular, the present invention provides for
Heat can be advantageously used to recover heat from high-temperature ash slurry obtained by washing water gas generated by partial oxidation of raw materials, which tends to clog the heat exchange means in conventional methods. Hereinafter, the present invention will be described with reference to the accompanying drawings. FIG. 1 is a flow sheet showing a preferred example of a process for implementing a method for recovering heat from high-temperature ash slurry generated in a coal partial oxidation process. In FIG. 1, water gas generated by partial oxidation of coal is introduced into cleaning device A from conduit 1,
After being washed with water introduced through a conduit 2 in this cleaning device A, the material is sent to the next step through a conduit 3. By cleaning the gas with water in cleaning device A,
Solids such as unburned carbon contained in the gas are dispersed in the wash water, and ash components such as sulfur, metals and heavy metals are dissolved or dispersed in the wash water in the form of various compounds. The generated high temperature ash slurry is sent to the first flashing device B through the conduit 4. The temperature of high temperature slurry is usually 100~300
within the range of ℃. The high-temperature ash slurry is flushed in the first flashing device B, and at least a portion of the water contained in the high-temperature ash slurry is converted into water vapor. Typically, flashing is performed by reducing the pressure. The pressure of this first flashing device B is
Normally, the amount of water vapor to be flashed and its temperature can be appropriately selected so as to be most advantageous for heat recovery. In the present invention, the flushing device is not particularly limited in shape or form as long as it can flush high-temperature ash slurry, for example, it has a rigid or horizontal cylindrical structure and has an internal structure. Examples include structures having a steam flash zone, a gas-liquid separation zone, and a slurry convection zone. The high temperature steam generated by the flash is sent to the heat exchange means D through the conduit 6. A cooling liquid is separately introduced into the heat exchange means D, and at least a part of the thermal energy possessed by the water vapor is recovered by heat exchange between the high temperature steam introduced into the heat exchange means D and the cooling liquid. As the cooling liquid, for example, any water such as a normal refrigerant, a liquid such as water used in other processes, water supplied to a boiler, etc. can be used. In addition, by providing an expansion turbine in place of the heat exchange means D, the thermal energy of the high-temperature steam can be recovered as motive energy. However, in general, as described below, the cleaning device A
The water used for gas cleaning is used. It is also possible to directly introduce the high-temperature ash slurry from which at least a portion of the water has been evaporated and removed by flashing in the first flashing device B into the solid-liquid separator M. As shown in the figure, it is practical to introduce this high-temperature ash slurry into the second flashing device C to flash it again, and then introduce it into the solid-liquid separation device M, considering the temperature of the ash slurry to be treated. The above is necessary, and furthermore, it is possible to flash in multiple stages. By flashing in multiple stages in this way, heat can be recovered more efficiently. An example of a two-stage flash will be described below. That is, the ash slurry introduced from the first flash device B to the second flash device C through the conduit 5 is flushed again to evaporate at least a portion of the water remaining in the ash slurry. The pressure of the second flashing device is selected so that the amount and temperature of flashing water vapor are suitable for heat recovery. However, since the pressure can only be lower than that of the first flashing device, and the amount of water vapor is greatly affected by the temperature of the first flashing device, the temperature of the first flashing device is usually taken into consideration when selecting the device. . The water vapor produced in the second flashing device is sent to the heat exchange means F through the conduit 7. In the present invention, as the second flash device, the same device as described above can be used. On the other hand, the ash slurry discharged from the second flashing device is introduced into the solid-liquid separation device M through the conduit 8 by a slurry pump 20 or the like. The ash slurry introduced into the solid-liquid separator M is separated into solids and water, the solids are discharged from the conduit 9, and the separated water is sent to the heat exchange means D through the conduit 10. It will be done. As mentioned above, the water vapor generated in the first flashing device is introduced into the heat exchange means D, and the water separated by the solid-liquid separator M is introduced into the cooling means D and then introduced from the first flashing device. By performing heat exchange with the water vapor, at least a part of the thermal energy of the water vapor is recovered. That is, the water separated by the solid-liquid separator M is heated, and the water vapor sent from the first flashing device is cooled. Due to the heat exchange in the heat exchange means D, the temperature of the water is usually 100 to 200°C.
The heated water is sent through conduit 2 to the scrubbing device A and is used again for scrubbing the gas. On the other hand, the water vapor cooled by the heat exchange means D is sent through the conduit 11 to the gas-liquid separation means J, where it is separated into water vapor and condensed water. The separated water vapor is sent through the conduit 12 to the heat exchange means E, where it exchanges heat with the cooling liquid. Then, the water vapor cooled to room temperature by the heat exchange means E is transferred to the conduit 1
3 to a gas-liquid separator K where the water is separated and the water vapor is discharged through conduit 14. As mentioned above, the water vapor generated in the second flashing device and sent to the heat exchange means F is cooled by exchanging heat with the cooling liquid there, and then passes through the conduit 15 to the gas-liquid separation device L. will be introduced in Here the water vapor and condensed water are separated and the water vapor is discharged through conduit 16. The water separated in the gas-liquid separators J, K and L is introduced into the solid-liquid separator M through conduits 17, 18 and 19, respectively. Any cooling liquid can be used in the heat exchange means E and F. Examples of cooling liquids include common refrigerants, liquids such as water used in other processes, water for boiler feed water, and the like. As mentioned above, in the heat recovery method of the present invention, the first flashing device may be used alone as the flashing device, and the third, fourth, etc. flashing devices may be arranged in the same manner. You can also. In addition, although the case is shown in which the heat exchange means D, E, and F are provided as the heat exchange means, and the gas-liquid separators J, K, and L are provided as the gas-liquid separator, the heat exchange means and the gas-liquid separator are additionally provided. can be placed. For example, the amount and pressure of water vapor to be discharged can be controlled by adjusting a valve placed at an arbitrary position in the conduit. In the present invention, commonly used devices can be used as the solid-liquid separator, heat exchange means, and gas-liquid separator. For example, a multi-tubular cylindrical heat exchanger or the like can be used as the heat exchange means. Next, examples of the present invention will be shown. Example 1 A cleaning device, two flushing devices, a solid-liquid separation device, three multi-tubular cylindrical heat exchangers, and three gas-liquid separation devices were arranged as shown in Figure 1 to prepare high-temperature ash slurry. The heat was recovered from the That is, a high-temperature ash slurry produced by washing water gas produced by partial oxidation of coal with water in a washing device A is introduced into a first flashing device B under reduced pressure to be flushed, and the generated water vapor is transferred to a multi-tube cylinder. type heat exchanger D. Water that has been separated from the high-temperature ash slurry by the solid-liquid separator M and is being circulated and used is introduced into the multi-tubular cylindrical heat exchanger D. The water vapor introduced into the multi-tubular cylindrical heat exchanger D was cooled using this circulating water, and the heat of the water vapor was used to heat the circulating water.
The heated circulating water was introduced into the cleaning device A. The cooled water vapor is discharged from the multi-tubular cylindrical heat exchanger D, introduced into the gas-liquid separator J, where the condensed water is separated, and the water vapor is further transferred to the multi-tubular cylindrical heat exchanger E.
After heat exchange with water used in other processes, the water was introduced into gas-liquid separator F. After separating the condensed water, the water vapor was discharged. On the other hand, the high-temperature ash slurry that had been flashed in the first flashing device was introduced into a second flashing device and flashed under reduced pressure. After introducing the generated steam into a multi-tubular cylindrical heat exchanger F and exchanging heat with water used in other processes,
The mixture was introduced into a gas-liquid separator L to perform gas-liquid separation, and the water vapor was discharged. The remaining high-temperature ash slurry is discharged from the second flashing device and sent to the solid-liquid separator M by a slurry pump, and this high-temperature ash slurry is separated into water and solids, and the separated water is separated as described above. It was introduced into a multi-tubular cylindrical heat exchanger D. Note that the water separated in the gas-liquid separators J, K, and L was introduced into the solid-liquid separator M. Table 1 shows the pressure, temperature, and composition of the fluid (water, steam, or high-temperature ash slurry) at the positions indicated by ~ in Figure 1. The water vapor introduced into the multi-tubular cylindrical heat exchangers D, E and F does not contain substantially any solids or dissolved impurities in the ash slurry, so it does not reach the inner walls of the tubes of the multi-tubular cylindrical heat exchangers. No adhesion of solid matter such as burnt carbon or dissolved impurities was observed at all. Therefore, troubles such as clogging of the multi-tubular cylindrical heat exchanger did not occur.

【table】

【table】 [Brief explanation of drawings]

FIG. 1 is a flow sheet showing a preferred example of a process for carrying out the method of recovering heat from high temperature ash slurry of the present invention. A: Cleaning device, B: First flush device, C:
Second flash device, D: First heat exchange means, E:
Second heat exchange means, F: Third heat exchange means, J: First gas-liquid separator, K: Second gas-liquid separator, L: Third gas-liquid separator, M: Solid-liquid separator, 1- 19: conduit, 20: slurry pump, ~: sample collection position.

Claims (1)

[Claims] 1. A gas produced by washing with water a gas containing solids obtained by oxidizing coal or hydrocarbons.
A high-temperature ash slurry having a temperature of 100°C or more is introduced into a flashing device and flashed to evaporate at least a portion of the water contained in the slurry, and the generated water vapor is introduced into a heat exchange means. The heat possessed by the water vapor is recovered by heat exchange with the cooling liquid introduced into the heat exchange means, and the remaining ash slurry flashed by the flashing device is discharged from the flashing device, and then transferred to the next flashing device. The water vapor generated by evaporating at least a part of the water remaining in the slurry is introduced into the heat exchange means, and the water vapor is exchanged with the cooling liquid introduced into the heat exchange means. A method for recovering heat from an ash slurry, the method comprising further recovering the heat possessed by the water vapor. 2. The method for recovering heat from an ash slurry as set forth in claim 1, wherein the temperature of the ash slurry introduced into the first flashing device is within the range of 100 to 300°C.