JP6566252B2 - Heat recovery method, heat recovery apparatus used therefor, and carbon dioxide separation and recovery method - Google Patents

Description

  The present invention relates to a heat recovery method, a heat recovery apparatus used therefor, and a carbon dioxide separation and recovery method. More specifically, in a factory or a steelworks where a plurality of heat sources exist, heat utilization equipment is efficiently and economically used from these heat sources. The heat recovery method and the heat recovery device used therefor can be recovered on the side, and the regeneration tower used when separating and recovering carbon dioxide by the chemical absorption method is used as a heat utilization facility to obtain the heat recovery method. The present invention relates to a method for separating and recovering carbon dioxide using the generated heat.

While global carbon dioxide (CO ₂ ) reduction is required, in addition to fundamental measures such as CO ₂ emission control and development of energy-saving technologies, technologies for separating and recovering emitted CO ₂ have been studied. ing.

In general, chemical absorption methods and physical adsorption methods are known as methods for separating and recovering CO ₂ . Of these, the chemical absorption method, was separated by absorbing CO ₂ in have been in the gas discharge with an alkaline absorption liquid amine solution such as, then, release the CO ₂ by heating the absorbent solution that has absorbed CO ₂ And collect CO ₂ . Incidentally, the absorbing liquid that has released the CO ₂ is returned to CO ₂ absorption ready again. This process is called regeneration, and the facility for regenerating the absorption liquid while heating the absorption liquid to recover CO ₂ is called a regeneration tower. The contact between the absorption liquid and the CO ₂ -containing gas is performed in an absorption tower, and CO ₂ is selectively absorbed by the absorption liquid.

Here, when recovering CO ₂ from an absorbing solution such as an amine solution, heating the absorbing solution using fossil fuel is not appropriate from the viewpoint of reducing CO ₂ . Therefore, it is ideal that the absorption liquid can be heated using existing heat. Patent Document 1 does not describe a specific form including the use of a heat medium as will be described later, but in a CO ₂ separation and recovery system using a steelworks facility, the exhaust from the sintered product cooler is not described. It is described that exhaust heat such as heat and hot stove exhaust gas is transported to a regeneration tower by a heat transport pipeline to heat the absorption liquid.

  In addition, as a technique related to heat transport, for example, heat medium oil is used as described in Non-Patent Document 1, or water (pressurized water) pressurized to a pressure higher than atmospheric pressure is used as described in Patent Document 2. There are ways to use it. Since the heat medium such as the heat medium oil and the pressurized water has fluidity, it is easy to transport the heat pipe. In addition, for example, in the case of a high-grade heat transfer oil such as a synthetic heat transfer oil, heat transport is possible up to a temperature range of about 300 ° C. Can be used as a heat medium cheaper than the heat medium oil. In addition, in the case of pressurized water, it is also possible to produce flash vapor by reducing the pressure at the destination.

  However, when heat transport is performed using a heat medium, a dangerous state due to overheating of the heat medium must be avoided. In other words, it is necessary to pay attention so that the temperature of the heat medium does not exceed the upper limit of the use temperature so as not to cause damage to the equipment. For this reason, for example, a spare tank can be provided so that an extra heat medium can be secured to cope with, or the equipment can be further strengthened or the pump power can be further enhanced so that the pressure of pressurized water can be increased to cope with high temperatures. Although it is conceivable, both of them will increase the equipment cost. In particular, when there are multiple heat sources in a large site such as a factory or steelworks, the total distance of the transportation piping to the heat-using equipment that uses heat, such as a regeneration tower, is long. Since a medium is required, the problem in terms of cost becomes extremely remarkable when a spare tank is provided. On the other hand, in order to prevent overheating of the heat medium, it is conceivable that a part of the exhaust heat is discharged without being recovered, but the heat that can be recovered originally is wasted.

On the other hand, as a process for separating and recovering CO ₂ by the chemical absorption method, generally, an absorbing solution (lean absorbing solution) such as an amine solution substantially free of CO ₂ is sprayed from the upper part of the absorption tower to contain CO _2. An absorption liquid (rich absorption liquid) that has absorbed CO ₂ from the gas is discharged from the bottom of the absorption tower. This rich absorbent is sent to the regeneration tower and sprayed from the top of the tower, and heated by steam or the like in a reboiler installed at the lower part of the regeneration tower to release CO ₂ . The released CO ₂ is recovered, and the lean absorbent having a reduced amount of CO ₂ is discharged from the bottom of the regeneration tower and used again for CO ₂ absorption. Such a chemical absorption method utilizes the characteristics of the absorption liquid such that the amount of CO ₂ absorbed is large at low temperatures and small at high temperatures. The rich absorption liquid discharged from the absorption tower is low temperature, and the regeneration tower Since the lean absorbent discharged from the reactor is at a high temperature, the rich absorbent is normally preheated by heat exchange with the lean absorbent before entering the regeneration tower, and is necessary for heating for regeneration of the absorbent. I try to reduce the amount.

Then, for example, using a heat pump, the heat generated when the absorption liquid absorbs CO ₂ in the absorption tower is recovered (see Patent Document 3), or the CO ₂ released in the regeneration tower is cooled. Therefore, a technique for recovering the heat used for condensing and separating the accompanying vapor component (see Patent Document 4) and using it for heating for regeneration of the absorbing solution has been studied. Also, the regeneration unit for regenerating the absorbent is divided into first and second, the first regeneration unit is heated by an external heating means, and the second regeneration unit is the heat of the gas released from the first regeneration unit. Steam for heating the absorption liquid by using a method for reducing the heat energy required for regeneration by using the sensible heat of exhaust gas that is subject to separation and recovery of CO ₂ (see Patent Document 5) It is also known to pre-heat a rich absorbent supplied to the regeneration tower (see Patent Document 6).

According to these methods, it is possible to reduce the amount of heat that needs to be supplied from the outside. However, in Patent Documents 3 and 4, the installation of a large heat pump and the running cost associated with its operation increase. In addition, the methods disclosed in Patent Documents 5 and 6 may not be able to sufficiently cover the amount of heat necessary for regeneration of the absorbing solution. In the CO ₂ separation and recovery process, for example, hot water used for district heating using the heat of saturated water after being used for heating by the reboiler of the regeneration tower or the heat of CO ₂ exhausted from the regeneration tower. Is known (see Patent Document 7), but does not reduce the amount of heat required for the CO ₂ separation and recovery process itself.

JP 2004-237167 A JP-A-1-234723 WO2011 / 122525 pamphlet WO2012 / 169634 pamphlet JP 2013-226476 A JP 2009-247932 A JP 2003-225537 A

Kunio Yoshida, Hideo Yoshida, Heat Exchanger Handbook, First Edition, Energy Conservation Center, Tokyo, 2005, pp. 309-318.

In recent years, the steel industry has set a goal of reducing CO ₂ emissions by about 30% by controlling CO ₂ emissions and separating and recovering CO ₂ as “Innovative Steelmaking Process Technology Development (COURSE50)”. (Http://www.jisf.or.jp/course50/index.html). Such efforts will be promoted in other manufacturing industries as well, and related technology development will become even more important. In particular, when CO ₂ is separated and recovered, CO ₂ is newly generated when energy is procured from outside for heating the alkaline absorbent such as amine solution. If the exhaust heat released in a dispersed manner is collected and transported, and heat can be recovered on the regeneration tower side and the exhaust heat can be effectively used, it is considered that the separation and recovery of CO ₂ is further promoted.

Under such circumstances, an object of the present invention is to provide a heat recovery method capable of recovering heat efficiently and economically from heat sources scattered in a site such as a factory or a steelworks. There is. Another object of the present invention is to provide a heat recovery apparatus capable of recovering heat efficiently and economically from these heat source facilities. Furthermore, another object of the present invention is to provide a method for separating and recovering CO ₂ that makes it possible to efficiently separate and recover CO ₂ by using the above heat recovery method.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors send out the heat medium to the scattered heat source sides, and return the heat medium obtained by heat exchange with the heat sources to the heat utilization equipment side. Thus, while recovering the heat of the heat medium on the heat utilization equipment side while circulating the heat medium, the flow rate of the heat medium to be circulated to each heat source is controlled according to the change in the heat amount at each heat source. The present inventors have found that heat can be recovered efficiently and economically by preventing overheating of the heat medium.

  In addition, in the above heat recovery, the present inventors provide a heat medium in which heat is recovered in the regeneration tower when the regeneration tower used when separating and recovering carbon dioxide by the chemical absorption method is used as a heat utilization facility. The present inventors have found that by preheating the absorption liquid discharged from the absorption tower using the heat, it is possible to reduce the heat energy necessary for the regeneration of the absorption liquid.

That is, the gist of the present invention is as follows.
(1) The exhaust heat exhausted as a gas with heat from a plurality of heat source facilities scattered in the premises of factories, steelworks, etc. is used as the heat source, and the heat source equipment side is connected to each heat source from these heat source sides. together to exit sends a heating medium independently for the heat medium to obtain a heat returned to the heat utilization facility side by heat exchange with the heat source, the heat medium between the heat source and the heat utilization facility side A heat recovery method for recovering the heat of the heat medium on the heat utilization equipment side while circulating,
The flow rate of exhaust heat gas at each heat source and / or the temperature of the exhaust heat gas is measured to detect the change in the heat amount of the exhaust heat at each heat source, and the heat medium according to the change in the heat amount of the exhaust heat at each heat source A heat recovery method characterized by controlling a flow rate of a heat medium to be circulated to each heat source for efficient heat recovery while preventing overheating .
(2) Comparing the temperatures of multiple heat sources, when the amount of heat of the high-temperature heat source with a high heat source temperature increases, at least a part of the heat medium circulating in the low-temperature heat source with a low heat source temperature The heat recovery as described in (1) above, while increasing the flow rate of the heat medium of the high-temperature heat source and decreasing the flow rate of the heat medium of the low-temperature heat source while keeping the overall flow rate of the circulating heat medium constant while distributing the heat flow to the high-temperature heat source Method.
(3) The heat recovery according to (2), wherein at least a part of the heat medium flowing through the lowest temperature heat source having the lowest heat source temperature is distributed to the highest temperature heat source having the highest temperature of the heat source. Method.
(4) When paying attention to the heat source with increased heat quantity among the multiple heat sources, among the remaining heat sources, from the low temperature heat source group consisting of low temperature heat sources whose temperature is lower than that of the heat source with increased heat quantity. One or more low-temperature heat sources are selected, and at least a part of the heat medium circulating in the low-temperature heat source is distributed to the heat quantity increasing heat source, and the overall flow rate of the circulating heat medium is made constant, while the heat quantity increasing heat source The heat recovery method according to (1), wherein the flow rate of the heat medium is increased and the flow rate of the heat medium of the low-temperature heat source is decreased.
(5) In the low temperature heat source group, the lowest temperature heat source having the lowest temperature of the heat source is selected, and at least a part of the heat medium circulating in the low temperature heat source is allocated to the heat quantity increasing heat source. Heat recovery method.
(6) The heat source is one or more types of exhaust heat selected from the group consisting of combustion exhaust gas, by-product gas generated in an ironworks, and cooling gas after being used for cooling high-temperature materials (1) The heat recovery method according to any one of to (5) .
(7) With respect to the heat medium that has obtained heat from each heat source, at least a part of the heat medium is not mixed with other heat mediums and is individually returned to the heat utilization equipment side as described in (1) to (6) above . The heat recovery method according to any one of the above.
(8) The heat recovery method according to any one of (1) to (7) , wherein the heat utilization facility is a regeneration tower used when carbon dioxide is separated and recovered by a chemical absorption method.

(9) Waste heat discharged as gas with heat from a plurality of heat source facilities scattered in the premises of factories, steelworks, etc. is used as a heat source , and these heat sources are connected to each heat source from the heat utilization facility side. together to exit sends a heating medium independently for the heat medium to obtain a heat returned to the heat utilization facility side by heat exchange with the heat source, the heat medium between the heat source and the heat utilization facility side A heat recovery device used to recover the heat of the heat medium on the heat utilization equipment side while circulating,
A heat medium that includes a delivery pipe that sends the heat medium from the heat utilization equipment side to each heat source , and a return pipe that returns the heat medium from the heat source to the heat utilization equipment side, and supplies the heat medium from the delivery pipe to each heat source Measure the flow rate of exhaust gas and / or the temperature of exhaust heat gas in each heat source, supply means, a heat exchanger that distributes the supplied heat medium to each heat source and obtains heat by heat exchange A heat quantity change detecting means for detecting a heat quantity change in each heat source, and for efficient heat recovery while preventing overheating of the heat medium according to the heat quantity change in each heat source detected by the heat quantity change detection means, A heat recovery apparatus comprising: a flow rate controller that adjusts each heat medium supply means to control a flow rate of the heat medium supplied to each heat source.
(10) heat change detection means, according to the a waste heat temperature instruments and / or waste heat flow rate measuring device for measuring the flow rate of the exhaust heat of the gas to measure the temperature of the exhaust heat of the gas (9) heat Recovery device.
(11) Two or more return pipes are arranged corresponding to the heat sources, and at least a part of the heat medium that has obtained heat from each heat source is individually mixed with the other heat medium without being mixed with the other heat medium. The heat recovery apparatus according to (9) or (10), which is returned.

(12) A method for separating and recovering carbon dioxide from a CO ₂ -containing gas containing carbon dioxide using the heat recovery method according to any one of (1) to (8) ,
Separation and recovery of carbon dioxide is a step of introducing a CO ₂ -containing gas and a lean absorbing liquid into an absorption tower and bringing them into contact with each other, and allowing the lean absorbing liquid to absorb carbon dioxide in the CO ₂ -containing gas to obtain a rich absorbing liquid; And introducing the rich absorption liquid discharged from the absorption tower into the regeneration tower and heating, separating carbon dioxide from the rich absorption liquid, and regenerating the lean absorption liquid.
The heat recovered from the heat medium by the heat recovery method is used for heating the rich absorption liquid in the regeneration tower, and the heat medium after the heat is recovered is used to preheat the rich absorption liquid discharged from the absorption tower. A method for separating and recovering carbon dioxide, comprising:

  According to the heat recovery method of the present invention, the heat of a heat source scattered in a site such as a factory or an ironworks can be recovered efficiently and economically on the heat utilization equipment side.

In addition, according to the method for separating and recovering carbon dioxide (CO ₂ ) in the present invention, it is possible to reduce the thermal energy necessary for regenerating the absorbing liquid, and CO ₂ can be separated and recovered efficiently.

FIG. 1 is a schematic explanatory diagram showing the distribution of heat sources in a model steelworks. FIG. 2 is a schematic explanatory view showing the flow rate variation of exhaust heat generated in the steelworks. FIG. 3 is a schematic explanatory view showing a state of temperature fluctuation of exhaust heat generated in the steelworks. FIG. 4 shows the relationship between the temperature of exhaust heat (exhaust gas temperature) generated at the model steelworks and the flow rate of exhaust heat (exhaust gas flow rate). FIG. 5 is an explanatory diagram schematically showing the state of heat recovery. FIG. 6 is another explanatory diagram schematically showing the state of heat recovery. FIG. 7 is still another explanatory view schematically showing the state of heat recovery. FIG. 8 is an explanatory view schematically showing a state of heat recovery from exhaust heat by the heat transfer oil in the first embodiment. FIG. 9 is an explanatory view schematically showing a state of heat recovery from exhaust heat by pressurized water in Example 2. FIG. 10 is a graph schematically showing the temperature dependence of the CO ₂ absorption amount of the absorbent used in the chemical absorption method. FIG. 11 is an explanatory diagram schematically showing a CO ₂ separation and recovery process according to the third embodiment. FIG. 12 is an explanatory diagram schematically showing a CO ₂ separation and recovery process according to the fourth embodiment. FIG. 13 is an explanatory view schematically showing a conventional CO ₂ separation and recovery process.

The present invention will be described in detail below.
In the present invention, a heat medium is sent out to a plurality of heat sources existing in a site such as a factory or a steelworks, and the heat medium obtained by heat exchange with the heat source is returned to the heat utilization equipment side so that the heat source and the heat When recovering the heat of the heat medium on the heat utilization equipment side while circulating the heat medium between the utilization facilities, the flow rate of the heat medium to be circulated to each heat source is changed according to the change in the heat amount at each heat source. Try to control. Specifically, a change in the amount of heat is detected in each heat source, and a part of the heat medium circulated to other heat sources is allocated to the heat source with the increased amount of heat.

Here, as shown in FIG. 1, for example, in a steelworks, slag sensible heat, hot water after granulated slag treatment, exhaust gas sensible heat discharged from a chimney, by-product in a vast site of 2 km × 3.5 km Even if sensible heat and other heat source equipment that is the source of the heat source is scattered, and heat utilization equipment such as a regeneration tower used for separation and recovery of CO2 is arranged almost in the center of this site, It can be seen that the heat transport distance from each heat source requires about 1 km. Also, in other manufacturing factories, as an example, in addition to heat sources such as pyrolysis furnaces and distillation towers in the chemical industry, processes for refining and rolling metals such as aluminum and copper, melting furnaces in the glass industry Various heat sources such as preheaters, kilns, coolers, etc. in the baking process of the float bath and cement industry are scattered throughout the factory premises. FIG. 1 is a layout diagram based on the model steelworks in the above-mentioned COURSE50 (consistent steelworks with a crude steel production of 8 million tons / year calculated by a field survey of integrated steelworks in Japan). In addition, in the figure, the names of equipment and processes are partially abbreviated, and those marked with ○ are the locations of the heat sources. Here, the darker the color of the circle, the higher the temperature of the heat source, and the larger the size of the circle, the greater the flow rate of the heat source (exhaust heat).

  FIG. 2 schematically shows how the flow rate of exhaust heat generated in the steel works fluctuates in a range exceeding ± 50% at the maximum depending on the operation state depending on the gas type. Furthermore, FIG. 3 also shows a state in which the temperature of exhaust heat generated in the steel works fluctuates in a range exceeding ± 20% at the maximum depending on the operation state depending on the gas type. As shown in these schematic diagrams, various types of exhaust heat generated at steelworks, exhaust heat generated in pyrolysis furnaces in the chemical industry, etc., change at least in flow rate and temperature, and the amount of heat constantly changes. .

  Generally, the amount of heat of exhaust heat generated in factories, steelworks, etc. can be expressed as “heat amount = temperature × flow rate × specific heat capacity × density”. Among these, for example, in the case of combustion exhaust gas or byproduct gas generated in an ironworks, the specific heat capacity is affected by the gas composition, and the density is affected by the pressure, composition, and temperature. However, if arranged in descending order of variation, “flow rate> temperature >> density to specific heat capacity”, and the heat quantity of exhaust heat can be roughly considered as “heat quantity minus temperature × flow rate”.

  On the other hand, in terms of the utility value of heat, it can be said that a heat source having a higher temperature has a higher value than a heat source having a lower temperature. Therefore, it is desirable to recover heat by giving priority to a heat source having a high temperature. FIG. 4 shows the relationship between the exhaust heat temperature (exhaust gas temperature) discharged from the COURSE 50 model steelworks and the exhaust heat flow rate (exhaust gas flow rate). According to this, the low temperature side is distributed in a wide range from about 100 ° C. to the high temperature side about 700 ° C., and the amount of exhaust heat at low temperature is large, and the amount of exhaust heat at high temperature is small. It turns out that there is a tendency. More specifically, Table 1 shows a representative example of exhaust heat generated at a steelworks. Here, the classification of the exhaust heat is based on a relative comparison of the temperatures of the exhaust heat generated in the steelworks. Of the types of exhaust heat, combustion exhaust gas is generated with combustion, such as exhaust gas after being used in a heating burner of a slab heating furnace. By-product gas is, for example, COG (Coke oven gas) is a gas that has calories and is actively reused in the steelworks after generation, and the cooling gas is a high-temperature material such as sintered ore in a sintering cooler, for example, air or It occurs when cooled with nitrogen.

Therefore, in the present invention, when exhaust heat exhausted as a gas having heat is used as a heat source, preferably, while measuring any one or more of the flow rate, temperature, density, or specific heat capacity of the exhaust heat, Preferably, while measuring either or both of the flow rate and / or temperature of the exhaust heat, a change in the heat amount of the exhaust heat is detected, and the exhaust heat that has increased in heat amount is distributed to other exhaust heat. A part of the medium should be distributed. Among them, from the viewpoint of preferentially collecting exhaust heat with high utility value, it is preferable to compare the temperature of multiple exhaust heat, and increase the amount of high-temperature exhaust heat with high exhaust heat temperature. In this case, at least a part of the heat medium circulating in the low-temperature exhaust heat whose exhaust heat temperature is low is distributed to the high-temperature exhaust heat, and the overall flow rate of the circulating heat medium is kept constant, It is preferable to increase the flow rate of the heat medium and decrease the flow rate of the heat medium for low-temperature exhaust heat. Most preferably, at least a part of the heat medium circulating in the lowest temperature exhaust heat with the lowest exhaust heat temperature is allocated to the highest temperature exhaust heat with the highest exhaust heat temperature. . Depending on the operating conditions of the heat source equipment or the like, for example, when the flow rate of the low-temperature exhaust heat is zero, not all of the heat medium may be allocated to the high-temperature exhaust heat side.

  Here, the high-temperature exhaust heat (high-temperature heat source) and the low-temperature exhaust heat (low-temperature heat source) are determined by relatively comparing the temperatures of the exhaust heat (heat source) existing in the system that performs heat recovery. In determining the temperature, for example, the temperature of the exhaust heat that is the target of heat recovery is averaged, and the temperature that is higher than the average value is defined as high-temperature exhaust heat, and the temperature that is lower than the average value is defined as low-temperature exhaust heat. High temperature exhaust heat and low temperature exhaust heat may be determined based on an intermediate value between the maximum value of the heat temperature and the minimum value of the exhaust heat temperature. Incidentally, the classification of high-temperature exhaust gas (high-temperature exhaust heat) and low-temperature gas (low-temperature exhaust heat) shown in Table 1 is based on an intermediate value (exhaust heat in the vicinity of the intermediate value is an intermediate temperature gas) ). Of course, for example, when a heat recovery system is configured only with exhaust heat classified as low-temperature gas, the exhaust heat temperature existing in the system is relatively compared based on the above-mentioned concept. And low-temperature exhaust heat.

  In addition, instead of using the average value or the intermediate value of the exhaust heat temperature as described above to compare the exhaust heat temperature relatively, or in combination with this, paying attention to the exhaust heat with increased heat, this You may make it distribute at least one part of a heat medium from the low-temperature exhaust heat whose exhaust heat temperature is lower than the heat amount increase exhaust heat. That is, when the total flow rate of the circulating heat medium is constant, focusing on the exhaust heat that has increased in heat quantity among the multiple exhaust heat that exists, the remaining exhaust heat has more than the focused heat increase exhaust heat. Select at least one low-temperature exhaust heat from a low-temperature exhaust heat group consisting of low-temperature exhaust heat having a low exhaust heat temperature, and distribute at least a part of the heat medium circulating in the low-temperature exhaust heat to the increased heat exhaust heat To. At this time, if there are two or more exhaust heats with increased heat quantity, at least one low-temperature exhaust heat group is selected from the corresponding low-temperature exhaust heat groups, and each heat medium is distributed to the increased heat quantity exhaust heat. do it. At this time, it is preferable to select the lowest temperature exhaust heat having the lowest exhaust heat temperature in the low temperature exhaust heat group.

  Fig. 5 schematically shows how heat is recovered from four heat sources (1a, 1a ': high-temperature exhaust heat, 1b: medium-temperature exhaust heat, 1c: low-temperature exhaust heat) for convenience. When the amount of heat of either heat 1a or 1a ′ increases, at least a part of the heat medium circulated to the low-temperature exhaust heat 1c may be distributed to high-temperature exhaust heat with an increased amount of heat. When the amount of heat of both the high-temperature exhaust heat 1a and 1a 'increases, the heat medium of the low-temperature exhaust heat 1c may be distributed to each, and the high-temperature exhaust heat 1a (exhaust heat temperature) with a higher exhaust heat temperature may be used. : 1a> 1a '), the heat medium may be distributed. In other words, for example, when the amount of heat of the high-temperature exhaust heat 1a ′ increases, at least one from the low-temperature exhaust heat group consisting of the medium-temperature exhaust heat 1b and the low-temperature exhaust heat 1c whose exhaust heat temperature is lower than the increased heat exhaust heat 1a ′. One low-temperature exhaust heat may be selected and at least a part of the heat medium circulating in the low-temperature exhaust heat may be distributed to the calorie increased exhaust heat 1a ′. At this time, preferably, the low-temperature exhaust heat 1c having the lowest exhaust heat temperature is selected from the low-temperature exhaust heat group, and the heat medium is distributed to the increased heat quantity exhaust heat 1a '.

  Moreover, there is no restriction | limiting in particular about the heat medium used by this invention, Well-known things, such as gas, such as water vapor | steam and air other than heat medium oil and pressurized water, can be used. As for the heat medium that has obtained heat by heat exchange in each heat source, as shown in FIG. 5, they may be collectively returned to the heat utilization equipment 2 side by one return pipe 3, or FIG. As shown in (in this example, there are three heat sources), for each heat source, or as shown in FIG. 7 (in this example, there are six heat sources), the temperature and flow rate of the heat source are adjusted, etc. A plurality of return pipes (4a, 4b, 4c) may be provided, and at least a part of the heat medium that has obtained heat from each heat source may be individually returned to the heat utilization equipment 2 side without being mixed with other heat mediums. . In particular, the examples shown in FIGS. 6 and 7 are suitable for a case where high-temperature heat is recovered as it is from a heat medium subjected to heat exchange with a high-temperature heat source having high utility value.

The heat recovered by the present invention can be used through appropriate processing depending on the type of heat utilization equipment, its form, and the like. For example, in the case of a regeneration tower used for separating and recovering CO ₂ by a chemical absorption method, steam is produced using a boiler, a flash tank or the like, and used for heating the absorbing solution. In this case, dry saturated steam is desirable as the steam to be used from the viewpoint of heating efficiency and the like. In the case of power generation using exhaust heat, the low boiling point medium is evaporated and the turbine is used for power generation. And the heat medium which collect | recovered heat | fever by the heat utilization equipment side is sent again to the heat source side, and is used for heat recovery. In addition, when a heat medium is pressurized water and a part of it is converted into steam in the flash tank and used for heating, the steam after use becomes return water and can be used again as a heat medium.

  In utilizing the heat recovery method of the present invention, for example, a heat recovery apparatus as shown in FIGS. 5 to 7 described above can be used. That is, the heat recovery apparatus of the present invention includes a delivery pipe 3 that sends out the heat medium from the heat utilization equipment 2 side to the heat source 1 side, and a return pipe 4 that returns the heat medium from the heat source 1 side to the heat utilization equipment 2 side. A heat medium is supplied to each heat source 1 by a heat medium supply means 5 such as a pump or a flow rate adjusting valve. The supplied heat medium is circulated to each heat source to obtain heat by the heat exchanger 6 and is returned to the heat utilization facility 2 side through the return pipe 4. In addition, each heat source 1 is provided with a heat amount change detecting means 7 for detecting a heat amount change of the heat source 1, and furthermore, a heat amount change in each heat source detected by these heat amount change detecting means 7. Accordingly, a flow rate controller 8 for adjusting each heat medium supply means 5 and controlling the flow rate of the heat medium supplied to each heat source 1 is provided.

  Here, regarding the heat amount change detection means 7, when the heat source is exhaust heat, specifically, an exhaust heat flow meter that measures the flow rate of exhaust heat or an exhaust heat temperature meter that measures the temperature of exhaust heat. In addition, to measure the density of exhaust heat, an arithmetic unit that calculates the density from the measurement results of pressure measuring instruments, temperature measuring instruments, composition measuring instruments, etc., and a temperature measuring instrument, composition to measure the specific heat capacity of exhaust heat An calculator or the like that calculates the specific heat capacity from the measurement result of a measuring instrument or the like can be exemplified. In particular, it is preferable that either one or both of the exhaust heat temperature measuring device and the exhaust heat flow measuring device is provided as the heat amount change detecting means 7. And the data regarding the calorie | heat amount change detected by the calorie | heat amount change detection means 7 are collected by the flow controller 8, and the flow volume of a heat medium required for every heat source is calculated. At this time, for example, if the amount of heat of the high-temperature heat source increases and a shortage of the heat medium is predicted, as described above, the heat medium that is circulated to other heat sources with respect to the heat source with the increased amount of heat. An instruction is given from the flow rate controller 8 to the heat medium supply means 5 in each heat source 1 so that a part of the heat medium is distributed, and the flow rate of the heat medium is controlled. Alternatively, when the heat quantity change detecting means 7 detects a heat quantity increase heat source having an increased heat quantity, among the remaining heat sources, at least one low temperature from a low temperature heat source group comprising a low temperature heat source having a heat source temperature lower than that of the heat quantity increase heat source. An instruction is issued from the flow controller 8 so that a heat source is selected and at least a part of the heat medium flowing through the low temperature heat source is distributed to the heat quantity increasing heat source.

  As shown in FIGS. 6 and 7, the heat recovery apparatus according to the present invention is provided with a plurality of return pipes (4a, 4b, 4c) corresponding to the heat sources, and obtains heat from each heat source. Further, at least a part of the heat medium may be individually transported to the heat utilization facility 2 side without being mixed with other heat medium. Furthermore, according to the utilization form of the collect | recovered heat | fever, for example, the heat utilization equipment 2 may be provided with apparatuses, such as a boiler and a flash tank, for producing steam.

In addition, the following method can be employed for separating and recovering CO ₂ from a CO ₂ -containing gas containing carbon dioxide (CO ₂ ) using the heat recovery method of the present invention. That is, the chemical absorption separation and recovery CO ₂ is the CO ₂ in the CO ₂ containing gas is absorbed in the absorbing solution and the rich absorption liquid to the lean absorption liquid by separating CO ₂ by heating the rich absorbing liquid I) a step of introducing a CO ₂ -containing gas and a lean absorbing liquid into an absorption tower and bringing them into contact with each other, and allowing the lean absorbing liquid to absorb carbon dioxide in the CO ₂ -containing gas to obtain a rich absorbing liquid And ii) introducing the rich absorption liquid discharged from the absorption tower into the regeneration tower and heating it to separate carbon dioxide from the rich absorption liquid to regenerate the lean absorption liquid. If the heat source equipment is a heat utilization facility, the heat recovery method of the present invention is used to send a heat medium to a plurality of existing heat sources and return the heat medium obtained by heat exchange to the regeneration tower side. Do not circulate the heat medium between Et al, to recover the heat of the heating medium in the regenerator side, use the heat to heat the rich absorbing liquid in the regeneration tower. In addition, the rich absorbent discharged from the absorption tower is preheated using the heat medium after the heat is recovered.

As described above, the chemical absorption method utilizes the characteristics of the absorbing solution such that the amount of CO ₂ absorbed is large at low temperatures and small at high temperatures. 10, the temperature dependency of the CO ₂ absorption amount of the absorbent is shown schematically, to absorb CO ₂ absorption solution at low temperature, the absorbing liquid that has absorbed CO ₂ (the rich absorbing liquid) carrying elsewhere, by the heating to high temperatures, it performs the recovery of CO ₂ in the CO ₂ desorbs (separated) from the absorption liquid. The absorption liquid (lean absorption liquid) from which CO ₂ has been diffused becomes a state capable of absorbing CO ₂ , returned to the absorption tower, and used again for absorption of CO ₂ .

That is, in the separation and recovery of CO ₂ by the chemical absorption method, as shown in FIG. 13, generally, an absorption liquid (lean absorption liquid) that does not substantially contain CO ₂ from the upper part of the absorption tower 12 into which the CO ₂ -containing gas 11 has been introduced. 13) is sprayed, and the absorption liquid (rich absorption liquid 14) that has absorbed CO ₂ from the CO ₂ -containing gas 11 is discharged from the bottom of the absorption tower 12. At this time, the CO ₂ -containing gas 11 from which CO ₂ has been removed is released as a purified gas 16. The rich absorbent 14 discharged from the absorption tower 12 is sent to the regeneration tower 17 and sprayed from the top of the tower, and heated by steam or the like in the reboiler 18 installed at the lower part of the regeneration tower 17. CO ₂ is released. The released CO ₂ is cooled by the cooler 19, and the accompanying vapor component is condensed and separated and recovered as CO ₂ gas 20. On the other hand, the lean absorbent 13 having a reduced amount of CO ₂ is discharged from the bottom of the regeneration tower 17 and is used again for absorbing CO ₂ . At this time, the lean absorbent 13 discharged from the regeneration tower 17 is high temperature, and the rich absorbent 14 discharged from the absorption tower 12 is low temperature. Before entering, the heat exchanger 21 exchanges heat with the lean absorbent 13 and preheats. As a result, the amount of heat necessary for heating the rich absorbent 14 in the regeneration tower 17 is reduced. Furthermore, the lean absorbent solution 13 is cooled by the cooler 15 before being introduced into the absorber 12, it is again used for the absorption of CO _2. In addition, by using steam such as a reboiler for heating in the regeneration tower 17, heating by steam condensation has a high heat transfer coefficient, so that the reboiler can be made compact, and steam condensation can be performed at a constant reboiler pressure. Since it always occurs at the same temperature, it is easy to control the temperature of the absorbent in the reboiler and to prevent denaturation of the absorbent with heat.

In contrast to such conventional CO ₂ separation and recovery, in the present invention, the heat recovered from the heat medium by the heat recovery method described above is used for heating the rich absorbent 14 in the regeneration tower 17 and the heat is recovered. The rich absorbing liquid 14 discharged from the absorption tower 12 is preheated by the heat medium after being applied. The heating of the rich absorbent 14 in the regeneration tower 17 is generally performed using steam or the like in a reboiler installed at the lower part of the regeneration tower 17. However, a heat medium that recovers heat by the heat recovery method of the present invention is used. When the steam is produced in a boiler, a flash tank, etc., and the rich absorbent 14 is heated in the reboiler using the produced steam, is the heating medium the same as the steam after the steam is produced in the boiler, the flash tank, etc. It has a higher temperature. Therefore, by using the heat of the heat medium after the steam production, the rich absorbent liquid 14 before being supplied to the regeneration tower 17 is heated, so that the regeneration tower 17 is used by the amount used as the temperature rising heat of the rich absorbent liquid 14. It becomes possible to reduce the amount of steam in the tank. That is, in the CO ₂ separation and recovery method according to the present invention, in addition to the conventional CO ₂ separation and recovery apparatus as shown in FIG. 13, the heat medium after the steam is produced by the reboiler or the like in the regeneration tower 17 and the regeneration tower 17. A heat exchanger (not shown) for exchanging heat with the rich absorbent 14 before being supplied to is further provided.

Examples of the absorption liquid to absorb CO _2, not particularly limited, monoethanolamine, diethanolamine, triethanolamine, other aqueous alkanolamine solution, such as methyldiethanolamine, can be used known ones such as ammonia. Moreover, CO ₂ a special restriction on CO ₂ containing gas for which the separation recovery is not, for example, coal, heavy oil, thermal power plants for natural gas or the like as fuel, boiler mill, cement plants kiln, coke Blast furnace at ironworks that reduces iron oxide, converter at the same steelworks that burns carbon from pig iron to produce steel, exhaust gas from coal gasification combined power generation facilities, natural gas at the time of mining, reformed gas, etc. Is mentioned. The carbon dioxide concentration in these CO ₂ -containing gases is usually about 5 to 30% by volume, although it depends on the gas species. Note that the CO ₂ -containing gas may contain a gas such as water vapor, CO, H ₂ S, COS, SO ₂ , NO ₂ , and hydrogen in addition to carbon dioxide.

  Hereinafter, the present invention will be specifically described based on examples. In addition, although calorific value calculation is mainly performed below, this invention is not limited to these contents.

Example 1
Combustion exhaust gas (exhaust temperature: 400 ° C) exhausted by burning fuel in a steel furnace at an ironworks and cooling gas (exhaust temperature: 200 ° C) after product cooling in the steel manufacturing process is used as a heat source. Using the method according to the present invention, heat recovery was performed using a regeneration tower for separating and recovering carbon dioxide (CO ₂ ) by a chemical absorption method as a heat utilization facility.

FIG. 8 shows the heat recovery apparatus used in the first embodiment. Here, the combustion exhaust gas is high-temperature exhaust heat 1a, and the cooling gas after cooling the product is low-temperature exhaust heat 1c. The regeneration tower 9 equipped with the heat medium oil boiler 10 is the heat utilization equipment 2, and heat medium oil (maximum use temperature 250 ° C.) is used as the heat medium, and the heat source 1 and the heat utilization equipment 2 Circulate between them.
This heat recovery device includes a delivery pipe 3 that sends out the heat transfer oil from the heat utilization equipment 2 side to the heat source 1 side, and a return pipe 4 that returns the heat transfer oil to the heat utilization equipment 2 side for each heat source (1a, 1c) (4a 4c), and heat medium oil is supplied to each heat source 1 from a delivery pipe 3 by a pump (heat medium supply means) 5 respectively. The supplied heat medium oil is heat-exchanged by the heat exchanger 6 in each heat source 1, and the heat medium oil that has obtained heat is returned to the heat utilization equipment 2 side through the high temperature return pipe 4a and the low temperature return pipe 4c, respectively. .

  Each heat source 1 includes an exhaust heat flow measuring device 7a for measuring the exhaust heat flow as a heat amount change detecting means 7 for detecting a heat amount change of the exhaust heat for each heat source (1a, 1c). The exhaust heat temperature measuring instrument 7b that measures the temperature is provided, and furthermore, the exhaust heat flow rate and temperature data measured by each heat source 1 are collected by these, and it is necessary for each heat source according to the heat amount change. A flow rate controller 8 is provided that calculates the flow rate of each heat transfer medium oil, controls the flow rate distribution of the heat transfer oil by giving instructions to the respective pumps 5, and controls the flow rate distribution.

Then, after the heat medium oil returned to the heat utilization equipment 2 side uses heat to produce steam in the heat medium oil boiler 10, the heat medium oil is again sent out to the heat source 1 side through the delivery pipe 3. The steam produced by such heat recovery is sent to the regeneration tower 9 and used for heating the absorbent (such as amine solution) (CO ₂ recovery). The steam used for heating is returned to the heat transfer oil boiler 10 as return water.

  Here, when the heat recovered under the conditions shown in Table 2 is rated, and the flow rate of the high-temperature exhaust heat 1a is increased by 50%, the heat recovery using the method according to the present invention is performed. Table 3 shows the state (flow rate, temperature), the state of the heat transfer oil (flow rate, temperature before and after heat recovery), and the amount of heat recovered. At this time, in order to satisfy the heat exchange conditions at the time of rating shown in Table 2, after determining the exhaust heat, the flow rate of the heat transfer oil, the flow path diameter, etc., the heat transfer to the heat exchanger is determined. The heat exchanger was designed by calculating the heat transfer coefficient from the prediction formula and calculating the length (size) required for the heat exchanger. Next, when the flow rate of exhaust heat and heat transfer fluid passed through this heat exchanger is changed to the conditions for increasing the flow rate of high-temperature exhaust heat shown in Table 3, the heat transfer coefficient determined from the heat transfer prediction formula is the initial design (rated Therefore, based on the heat transfer coefficient and the size of the heat exchanger to be used, the amount of heat exchanged and the temperature of each heat transfer oil after the heat exchange are determined.

  In Tables 2 and 3, the values used when the flow rate of the exhaust heat and the flow rate of the heat transfer oil are made relative to each other are unified with the flow rate of the high-temperature exhaust heat 1a shown in Table 2. Further, the values used for relativizing the recovered heat amount are unified with the recovered heat amount on the high-temperature exhaust heat 1a side at the time of rating shown in Table 2. In other words, here, heat exchanger oil temperatures of 250 ° C. on the high-temperature exhaust heat 1a side and 150 ° C. on the low-temperature / low-temperature exhaust heat 1c side are used under rated conditions. The heat medium oil flow rate is controlled (flow rate increased) so that the heat medium oil temperature on the high-temperature exhaust heat 1a side is maintained at 250 ° C. when the heat 1a flow rate increases by 50%. At that time, as the flow rate of the heat transfer oil on the high-temperature exhaust heat 1a side is increased, the flow rate of the heat transfer oil to the low-temperature exhaust heat 1c side decreases, and as a result, the heat transfer oil on the low-temperature exhaust heat 1c side The temperature has risen to 152 ° C.

When the high-temperature exhaust heat flow rate shown in Table 3 is increased by 50%, the flow controller 8 adjusts the pump 5 on the high-temperature exhaust heat 1a side and the pump 5 on the low-temperature exhaust heat 1c side. While the flow rate of heat transfer oil has increased (0.5 → 0.7) and the flow rate of heat transfer oil with low-temperature exhaust heat 1c has decreased (4.5 → 4.3), the total amount of heat transfer oil in this system has increased. There is no change.
On the other hand, paying attention to the amount of heat recovered, by applying the present invention as shown in Table 3, the total amount of heat recovered by the heat utilization facility 2 is from 4.00 at the rated time to 4.37. It can be seen that it increases greatly. In addition, the maximum use temperature (250 ° C.) of the heat transfer oil is maintained, and the usefulness of the present invention can be confirmed.

  Further, when the flow rate of the high-temperature exhaust heat 1a is increased by 50%, if the method of the present invention is not applied, the results are as shown in Table 4 below. That is, in order not to exceed the upper limit (250 ° C) of the operating temperature of the heat transfer oil, it is necessary to throw away the increased amount of the high-temperature exhaust heat 1a without passing through the heat exchanger (dissipate to the atmosphere) As a result, the amount of heat recovered does not change compared to the rated time.

(Example 2)
By-product gas (exhaust temperature: 600 ° C) in the steel manufacturing process of steelworks, combustion exhaust gas (exhaust temperature: 400 ° C) emitted by burning fuel in the steel heating furnace, and product cooling in the same steel manufacturing process Heat recovery using the method according to the present invention, with the later cooling gas (discharge temperature: 170 ° C) as the heat source and pressurized water (the maximum operating temperature is limited to 180 ° C for reasons of equipment) as the heat medium went.

FIG. 9 shows a heat recovery apparatus used in the second embodiment. Here, on the basis of an intermediate value (335 ° C.) between the maximum temperature and the minimum temperature of the heat source, the by-product gas and the combustion exhaust gas are regarded as high-temperature exhaust heat (by-product gas 1a, combustion exhaust gas 1a ′: temperature 1a> 1a ′), the cooling gas after cooling the product is defined as low-temperature exhaust heat 1c. Moreover, the regeneration tower 9 equipped with the flash tank 11 is used as the heat utilization facility 2, and the pressurized water obtained from each heat source is supplied to the heat utilization facility 2 side through the high temperature return pipe 4a, the high temperature return pipe 4a ', and the low temperature return pipe 4c, respectively. Returned to Other than these, it is the same as the heat recovery apparatus in the first embodiment. A part of the pressurized water returned to the heat utilization equipment 2 side is converted into steam in the flash tank and sent to the regeneration tower 9 to be used for heating the absorbing solution such as amine solution (CO ₂ recovery). . The steam used for heating becomes return water, is pressurized by a pressure pump (not shown), and is used again as a heat medium. Further, the pressurized water that has not been converted into steam in the flash tank is again used for heat recovery as a heat medium.

  Here, when the heat recovered under the conditions shown in Table 5 is rated, the flow rate of the high-temperature exhaust heat 1a is increased by 50%, and the flow rate of the high-temperature exhaust heat 1a ′ is increased by 30%. Table 6 shows the state of exhaust heat (flow rate, temperature), the state of pressurized water (flow rate, temperature before and after heat recovery), and the amount of heat recovered for heat recovery using the method. Note that the values used when the flow rate of the exhaust heat and the flow rate of the pressurized water are made relative to each other are unified with the flow rate of the high-temperature exhaust heat 1a at the time of rating shown in Table 5, as in the first embodiment. In addition, the value used when the recovered heat quantity is made relative is unified with the recovered heat quantity on the high temperature exhaust heat 1a side at the time of rating shown in Table 5.

When the flow rate of the high-temperature exhaust heat shown in Table 5 is increased (1a: 50% increase, 1a ': 30% increase), the flow controller 8 controls the high-temperature exhaust heat 1a, high-temperature exhaust heat 1a', and low-temperature exhaust heat 1c. By adjusting the pumps 5 respectively, the flow rate of the heat transfer oil (0.5 → 0.7) of the high temperature exhaust heat 1a and the flow rate of the heat transfer oil (2.8 → 3.4) of the high temperature exhaust heat 1a 'are increased compared to the rated time. At the same time, the flow rate (4.8 → 4.0) of the heat transfer oil for the low-temperature exhaust heat 1c has decreased, but the total amount of heat transfer oil in this system has not changed.
On the other hand, focusing on the amount of heat recovered, by applying the present invention as shown in Table 5, the total amount of heat recovered by the heat utilization facility 2 is from 12.03 at the rated time to 13.32. It can be seen that it increases greatly. Moreover, the maximum use temperature (180 ° C.) of the pressurized water is maintained, and the usefulness of the present invention can be confirmed.

  Further, when the flow rate of the high-temperature exhaust heat is increased, if the method of the present invention is not applied, the results are as shown in Table 7 below. That is, in order not to exceed the upper limit (180 ° C) of the operating temperature of the pressurized water, the increase in the high-temperature exhaust heat 1a and the high-temperature exhaust heat 1a 'is discarded without passing through the heat exchanger (dissipated to the atmosphere). As a result, the amount of heat recovered will not change compared to the rated time.

As described above, according to the present invention, heat can be efficiently and economically recovered while preventing overheating of the heat medium. In particular, even when a plurality of heat sources are scattered in a large site such as a factory or a steelworks, heat can be recovered on the heat utilization equipment side while suppressing an increase in cost. Therefore, for example, when separating and collecting CO ₂ , it is possible to collect and transport the exhaust heat released in a dispersed manner in factories or steelworks, etc., and recover the heat on the regeneration tower side. Can be effectively used.

(Example 3)
Utilizing the heat recovery method shown in Example 1, it was subjected to separation and recovery of CO ₂ from CO ₂ containing gas. FIG. 11 is an explanatory diagram schematically showing a CO ₂ separation and recovery process according to the third embodiment. Although the absorption tower portion is omitted, an absorption liquid (lean absorption liquid 13) substantially free of CO ₂ is sprayed from the upper part of the absorption tower into which a CO ₂ -containing gas such as blast furnace gas (BFG) is introduced, and CO 2 ₂ absorbent having absorbed CO ₂ -containing gas (rich absorbing liquid 14) is discharged from the bottom of the absorption column, the points of CO ₂ containing gas from which CO ₂ has been removed is discharged as purified gas, 13 This is the same as the conventional CO ₂ separation and recovery process shown in FIG.

In the CO ₂ separation and recovery process according to the third embodiment, the rich absorbent 14 discharged from the absorption tower (not shown) enters the lean absorbent 13 in the first heat exchanger 21 before entering the regeneration tower 17. And heat exchange with the heat medium 22 after the heat necessary for heating the rich absorbent 14 in the regeneration tower 17 is recovered by the second heat exchanger 23 and preheating. And introduced into the regeneration tower 17. That is, the heat medium 22 that has recovered heat from each heat source 1 by the heat recovery method as shown in the first embodiment, after producing steam with a boiler 24 equipped with a economizer, partly directly on the heat source 1 side. The remainder is sent to the second heat exchanger 23, exchanged with the rich absorbent 14 before being introduced into the regeneration tower 17, and then returned to the heat source 1 side.

On the other hand, the steam 25 produced by the boiler 24 is sent to the reboiler 18 installed at the lower part of the regeneration tower 17. Then, the rich absorbent 14 preheated by the second heat exchanger 23 is sent to the regeneration tower 17 and sprayed from the top of the tower, heated by steam from the reboiler 18, and regenerated to the lean absorbent 13. . The lean absorption liquid 13 is discharged from the bottom of the regeneration tower 17 and sent to an absorption tower (not shown) to be used again for CO ₂ absorption. The CO ₂ discharged from the regeneration tower 17 is cooled by a cooler 19. Upon cooling, the accompanying vapor component is condensed and separated and recovered as CO ₂ gas 20.

Here, heat is recovered by the heat recovery method of Example 1 using heat transfer oil as the heat transfer medium, steam is produced by the boiler 24 equipped with a economizer, and the steam is sent to the reboiler 18 to regenerate the tower. was recovered CO ₂ gas 20 is heated 17 rich absorbing solution of (rich amine solution). Moreover, 80% by volume of the heat transfer oil 22 after the steam is produced by the boiler 24 equipped with a economizer is sent to the second heat exchanger 23 before being introduced into the regeneration tower 17. The rich absorbent solution (rich amine solution) 14 was preheated. At this time, the heat medium oil 22 recovered from the heat by the heat recovery method is used in steam production in the boiler and the temperature is lowered to about 125 ° C., and further, the heat medium oil 22 is supplied to the boiler in the economizer. As a result of being used to raise the temperature of the water to be evaporated in step 1, the heat medium oil 22 is used to preheat the rich amine solution 14 in the second heat exchanger 23.

And under the conditions shown in Table 8, the temperature of the rich amine solution 14 is increased from 79 ° C. to 93 ° C. by heat exchange by the second heat exchanger 23, and the heat transfer oil is heated from 120 ° C. to 101 ° C. Until the temperature dropped. This preheating amount is 0.5 GJ per CO ₂ unit recovery amount. In general, since the heat intensity necessary for the regeneration of the amine solution is 2.0 to 4.0 GJ, it is considered that it can greatly contribute to the saving of steam necessary for the heating.

Example 4
Utilizing the heat recovery method shown in Example 2, it was subjected to separation and recovery of CO ₂ from CO ₂ containing gas. FIG. 12 is an explanatory view schematically showing the CO ₂ separation and recovery process according to the fourth embodiment, and the absorption tower portion is omitted as in FIG.

In the CO ₂ separation and recovery process according to the fourth embodiment, the pressurized water 26 that has recovered heat from the heat sources 1 by the heat recovery method as shown in the second embodiment, Become. The entire amount (100%) of the return water is sent to the second heat exchanger 23 and exchanged with the rich absorbent solution (rich amine solution) 14 before being introduced into the regeneration tower 17, and then returned to the heat source 1 side. Returned. At this time, it is assumed that the pressurized water 26 recovered from the heat by the heat recovery method is separated into 115 ° C. steam and 115 ° C. pressurized water in the flash tank 27. The exchanger 23 is used for preheating the rich amine solution 14.
Note that any water returned to the heat source 1 side is pressurized by a pressure pump (not shown) and circulated as pressurized water. In this way, heat was recovered by the heat recovery method of Example 2 using pressurized water as a heat medium, and the rich amine solution 14 before being introduced into the regeneration tower 17 was preheated as in Example 3.

Then, under the conditions shown in Table 9, the temperature of the rich amine solution 14 is increased from 79 ° C. to 84 ° C. by the heat exchange by the second heat exchanger 23, and the pressurized water is heated from 115 ° C. to 110 ° C. Declined. This preheating amount is 0.2 GJ per CO ₂ unit recovery amount. As described above, since the heat intensity necessary for regeneration of the amine solution is generally 2.0 to 4.0 GJ, it is considered that it can greatly contribute to the saving of steam necessary for heating.

1: heat source, 1a, 1a ′: high temperature exhaust heat, 1b: medium temperature exhaust heat, 1c: low temperature exhaust heat, 2: heat utilization equipment, 3: delivery piping, 4: return piping, 5: heat medium supplying means, 6: Heat exchanger, 7: heat quantity change detecting means, 8: flow rate controller, 9: regeneration tower, 10: heat transfer oil boiler, 11: gas containing CO ₂ , 12: absorption tower, 13: lean absorption liquid, 14: rich absorption Liquid, 15: cooler, 16: purified gas, 17: regeneration tower, 18: reboiler, 19: cooler 19, 20: CO ₂ gas, 21: heat exchanger (first heat exchanger), 22: heat Medium, 23: heat exchanger (second heat exchanger), 24: economizer and boiler, 25: steam, 26: pressurized water, 27: flash tank.

Claims (12)

Exhaust heat exhausted as gas with heat from multiple heat source facilities scattered around the premises of factories, steelworks, etc. is used as the heat source. together to leave the feed heat medium in the heat medium to obtain a heat by heat exchange with the heat source so as to return to the heat utilization equipment side, while the heat medium is circulated between each heat source and the heat utilization facility side A heat recovery method for recovering the heat of the heat medium on the heat utilization equipment side,
The flow rate of exhaust heat gas at each heat source and / or the temperature of the exhaust heat gas is measured to detect the change in the heat amount of the exhaust heat at each heat source, and the heat medium according to the change in the heat amount of the exhaust heat at each heat source A heat recovery method characterized by controlling a flow rate of a heat medium to be circulated to each heat source for efficient heat recovery while preventing overheating .   Comparing the temperatures of multiple heat sources relative to each other, when the amount of heat from a high-temperature heat source with a high heat source temperature is increased, at least part of the heat medium circulating in the low-temperature heat source with a low heat source temperature is used as the high-temperature heat source. The heat recovery method according to claim 1, wherein the flow rate of the heat medium of the low temperature heat source is decreased while the flow rate of the heat medium of the low temperature heat source is increased while increasing the flow rate of the heat medium of the high temperature heat source while keeping the overall flow rate of the circulating heat medium constant.   The heat recovery method according to claim 2, wherein at least a part of the heat medium circulating in the lowest temperature heat source having the lowest temperature of the heat source is distributed to the highest temperature source having the highest temperature of the heat source.   When paying attention to the heat source with increased heat quantity among the plurality of heat sources, one or more from the low-temperature heat source group consisting of low-temperature heat sources whose heat source temperature is lower than that of the heat source with increased heat quantity among the remaining heat sources. Select a low-temperature heat source and distribute at least a part of the heat medium flowing through the low-temperature heat source to the heat-increased heat source. The heat recovery method according to claim 1, wherein the flow rate is increased and the flow rate of the heat medium of the low-temperature heat source is reduced.   The heat recovery method according to claim 4, wherein the lowest temperature heat source having the lowest temperature of the heat source is selected from the low temperature heat source group, and at least a part of the heat medium flowing through the low temperature heat source is distributed to the heat quantity increasing heat source. . Heat source, combustion exhaust gas generated in steelworks, by-product gas, and any of claims 1 to 5 is one or more waste heat selected from the group consisting of cooling gas after used for cooling the hot product A heat recovery method according to any one of the above. The heat according to claim 1 , wherein at least a part of the heat medium obtained from each heat source is individually returned to the heat utilization facility without being mixed with the other heat medium. Collection method. The heat recovery method according to any one of claims 1 to 7 , wherein the heat utilization facility is a regeneration tower used when carbon dioxide is separated and recovered by a chemical absorption method. Exhaust heat exhausted as gas with heat from multiple heat source facilities scattered around the premises of factories, steelworks, etc. is used as the heat source. together to leave the feed heat medium in the heat medium to obtain a heat by heat exchange with the heat source so as to return to the heat utilization equipment side, while the heat medium is circulated between each heat source and the heat utilization facility side , A heat recovery device used to recover the heat of the heat medium on the heat utilization equipment side,
A heat medium that includes a delivery pipe that sends the heat medium from the heat utilization equipment side to each heat source , and a return pipe that returns the heat medium from the heat source to the heat utilization equipment side, and supplies the heat medium from the delivery pipe to each heat source Measure the flow rate of exhaust gas and / or the temperature of exhaust heat gas in each heat source, supply means, a heat exchanger that distributes the supplied heat medium to each heat source and obtains heat by heat exchange A heat quantity change detecting means for detecting a heat quantity change in each heat source, and for efficient heat recovery while preventing overheating of the heat medium according to the heat quantity change in each heat source detected by the heat quantity change detection means , A heat recovery apparatus comprising: a flow rate controller that adjusts each heat medium supply means to control a flow rate of the heat medium supplied to each heat source. The heat recovery apparatus according to claim 9 , wherein the heat quantity change detecting means is an exhaust heat temperature measuring device that measures the temperature of exhaust heat gas and / or an exhaust heat flow meter that measures the flow rate of exhaust heat gas . Billing return pipe is disposed more to correspond to the heat source, at least a portion of the heat medium to obtain a heat each heat source, which is returned to the heat utilization equipment-side individually without being mixed with other heat medium Item 11. The heat recovery apparatus according to Item 9 or 10 . A method for separating and recovering carbon dioxide from a CO ₂ -containing gas containing carbon dioxide using the heat recovery method according to claim 1 ,
Separation and recovery of carbon dioxide is a step of introducing a CO ₂ -containing gas and a lean absorbing liquid into an absorption tower and bringing them into contact with each other, and allowing the lean absorbing liquid to absorb carbon dioxide in the CO ₂ -containing gas to obtain a rich absorbing liquid; And introducing the rich absorption liquid discharged from the absorption tower into the regeneration tower and heating, separating carbon dioxide from the rich absorption liquid, and regenerating the lean absorption liquid.
The heat recovered from the heat medium by the heat recovery method is used for heating the rich absorption liquid in the regeneration tower, and the heat medium after the heat is recovered is used to preheat the rich absorption liquid discharged from the absorption tower. A method for separating and recovering carbon dioxide, comprising:

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