JP2009243862A - Method of controlling prevention for blocking in heat exchanger - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To find out a principle of generating blocking in a heat exchanger 30 during a manufacturing process of gas hydrate; to provide operation conditions and a control method having high efficiency of cooling and generating no blocking in the heat exchanger 30; and to provide a highly efficient continuous operation control method of the heat exchanger 30 from the operation conditions and the control method. <P>SOLUTION: In the heat exchanger for cooling hydrate slurry, a blocking pattern map for indicating the presence of blocking in the heat exchanger is obtained beforehand by using two parameters of Reynolds number and a supercooling degree based on a three-phase parallel condition, and the control is carried out while the blocking is not generated on the pattern map. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention, for example, in a gas hydrate manufacturing process in which a gas hydrate is manufactured by reacting a raw material gas such as natural gas with water, is caused by hydrate formation and adhesion in a heat exchanger that cools the liquid phase. The present invention relates to a control method for preventing the generated heat exchanger from being blocked.

  In recent years, as a safe and economical means for transporting and storing natural gas and the like, a method using gas hydrate obtained by hydrating natural gas to form a solid state hydrate has attracted attention.

  In general, a gas hydrate is an ice-like solid crystal consisting of water molecules and gas molecules produced by reacting a raw material gas with raw material water at low temperature and high pressure. It is a general term for clathrate hydrate (hydrate) in which gas molecules are present inside (cage).

Natural gas hydrate contains about 165 Nm ^{3 of} natural gas in 1 m ³ of gas hydrate. For this reason, research and development using gas hydrate as a means for transporting and storing natural gas has been actively conducted.

  Advantages of hydrating natural gas include: (a) the natural gas hydrate has an equilibrium temperature condition under atmospheric pressure of −80 ° C. (193 K) or less, so that liquefied natural gas (LNG) that has already been put into practical use is used. ) Under atmospheric pressure storage and transportation temperature (-163 ° C. (110 K)), storage and transportation are possible, (b) In addition, as described above, large natural gas hydrate Since the equilibrium temperature condition under atmospheric pressure is −80 ° C. (193 K) or less, the durability and heat insulation of storage and transportation facilities can be greatly simplified.

  Natural gas hydrate is known to exist in a relatively stable state even outside equilibrium conditions because it has a special performance called a self-preservation effect. A transparent ice film is formed on the surface of natural gas hydrate in a self-preserving state, and it is becoming clear that this ice film expresses self-preserving properties.

  According to this self-preserving effect, the amount of natural hydrate decomposed in the vicinity of −20 ° C. (253 K) is the smallest, and by utilizing this phenomenon, natural gas hydrate can be stored in a relatively stable state, and can be stored and transported. It is possible to greatly reduce the cost required for the operation.

  Furthermore, the gas hydrate obtained in the gas hydrate production step is in the form of a slurry containing about 40 to 60% by weight of moisture. Therefore, the gas hydrate is increased to about 90 wt% by dehydration or regeneration, and compression molding is performed under atmospheric pressure or high pressure conditions to form a molded product or block shape such as an almond shape, a lens shape, a spherical shape, or an indefinite shape. It is made easy to store by processing into a large molded article.

  Here, as shown in FIG. 8, the hydrate manufacturing process for generating a slurry-like gas hydrate is performed by using a gas raw material (for example, natural gas) and a water raw material (for example, water) supplied to the hydrate generating tank 44. In order to remove the generated heat generated at that time, the heat exchanger 30 is circulated by the slurry pump 43 and cooled, whereby the hydrate is manufactured. For example, in the production of natural gas hydrate, undercooling is performed to the production conditions (pressure is 5 MPa, temperature is 5 ° C. or less), and the raw material gas and the raw water are agitated, etc. It is done by contacting.

  The hydrate slurry produced in the hydrate production tank 44 is circulated through the heat exchanger 30 to remove the produced heat generated during production. A part of the slurry is supplied from a hydrate slurry circulation line 45 to a hydrate processing (dehydration and molding) process.

  Here, there is a problem that hydrate is generated and adhered in the heat exchanger 30 that cools the hydrate slurry, and the heat exchanger 30 is blocked. When the heat exchanger 30 is blocked, the hydrate that causes the blockage is melted by an operation of releasing the blockage such as heating the heat exchanger 30, and the hydrate manufacturing process is stopped during that time. After the heat exchanger 30 is heated, re-cooling is required, so that energy efficiency is lowered, and time for releasing the blockage is also required.

  In addition, it is difficult to confirm the state of the hydrate blocking the inside of the heat exchanger 30 at the time of the block release operation, and much time and energy are required to realize the reliable block release. is there.

  FIG. 6 shows a system diagram in which two heat exchangers 30 are connected in parallel to the hydrate production tank 44 and hydrate production is possible even when the clogging release operation is performed. During normal operation, the hydrate slurry is sent from the hydrate production tank 44 through the open valve 49a to the heat exchanger 30a by the slurry pump 43 and circulated.

  When blockage of the heat exchanger 30a is detected by a flow meter 36 such as a Coriolis mass flow meter installed on the hydrate slurry circulation line 45, the valve operation is performed so that the hydrate slurry circulates through the heat exchanger 30b. Do. While the hydrate slurry is circulated through the heat exchanger 30b and cooling is performed, the heat exchanger 30a performs the blocking release operation.

  FIG. 7 shows a system diagram of refrigerant circulation in the heat exchanger 30, and a refrigerant (brine) 28 such as ethylene glycol cooled in the low-temperature thermostat 42 is sent to the heat exchanger 30 via the pump 51, and the brine It is configured to circulate through a refrigerant circulation line 46 constituted by the transport pipe 29. The blockage release operation of the heat exchanger 30 raises the temperature of the low temperature thermostatic chamber 42 to a temperature at which the hydrate slurry blocking the inside of the heat exchanger 30 is melted, and the heated refrigerant is transferred to the heat exchanger 30. It is done by circulating it.

  By designing the hydrate manufacturing process as described above, it is possible to continue manufacturing hydrate even during the operation of releasing the blockage of the heat exchanger 30. However, the other heat exchanger 30 may be clogged during the operation of releasing the clogging of the heat exchanger 30, and a large amount is used for raising the temperature of the low-temperature thermostatic chamber 42 of the refrigerant circulation system and for recooling after the clogging is released. It can be said that energy is needed and there are still problems to be solved. On the other hand, the invention which prevents obstruction | occlusion of the heat exchanger 30 is performed (for example, refer patent document 1).

According to the invention described in Patent Document 1, ice slurry, which is a cooled object having a content of seed ice particles of 5% to 15%, is circulated in the heat exchanger 30 so that the ice is focused on the seed ice particles. Therefore, it is possible to prevent ice from growing on the inner wall surface of the heat transfer tube of the heat exchanger 30 and blocking the heat exchanger 30.
JP 7-19682 A

  However, since the method described in Patent Document 1 uses an ice slurry as a cooling target, it cannot be used for cooling a gas hydrate. In other words, ice slurry is cooled by making water, freezing relaxant (sorbitol, etc.) and ice below 0 ° C. under atmospheric pressure, whereas gas hydrate is manufactured at low temperature and high pressure. The cooling conditions of the heat exchanger 30 are greatly different for cooling the gas hydrate slurry using three phases of gas, water and ice as raw materials. For example, the conditions for producing natural gas hydrate are a temperature of about 6 ° C. and a pressure of about 5 MPa. The situation where clogging occurs in the heat exchanger 30 is significantly different from that of ice slurry, and the clogging conditions are not yet met. It has not been revealed.

  Further, in the heat exchanger 30, the larger the temperature difference between the refrigerant and the object to be cooled, the higher the heat transfer efficiency and the higher the efficiency. For this reason, for the most efficient operation of the heat exchanger 30, the operating condition in the state of being cooled to just before the blockage is desirable, but it is difficult to detect the state just before the blockage, and the state is maintained. However, the operation of the heat exchanger 30 is not realized.

  Therefore, the present invention has been made to solve the above-mentioned problems, and investigated the principle that the heat exchanger 30 is blocked in the gas hydrate manufacturing process, so that the heat exchanger 30 is not blocked. It is another object of the present invention to provide an operation condition and control method with high cooling efficiency, and to provide a highly efficient continuous operation control method for the heat exchanger 30 based on the operation condition and control method.

  In order to solve the above-described problem, the heat exchanger blockage prevention control method according to the invention described in claim 1 is the heat exchanger 30 for cooling the hydrate slurry, and the degree of supercooling from the Reynolds number and the three-phase parallel condition. The block pattern pattern 39 representing the presence or absence of blockage of the heat exchanger 30 is obtained in advance using these two parameters, and control is performed on the pattern map 39 under the condition that no blockage occurs.

  The heat exchanger blockage prevention control method according to the invention of claim 2 is a heat exchanger 30 that cools a liquid phase in a gas hydrate manufacturing process, and heat exchange by generation and adhesion of a hydrate slurry that is an object to be cooled. This is a control method for preventing the device blockage 30, characterized in that control is performed using the blockage pattern map 39.

  According to a third aspect of the present invention, there is provided a heat exchanger blockage prevention control method that calculates an overall heat transfer coefficient from the temperature and flow rate of the hydrate slurry 68 and refrigerant at the inlet and outlet of the heat exchanger 30, and The thickness of the hydrate layer 26 formed in the heat exchanger 30 is calculated from the decrease in the overall heat transfer coefficient accompanying the operation of the exchanger 30, and the thickness of the hydrate layer 26 and the block pattern pattern 39 are calculated. Control is performed based on this.

  The heat exchanger blockage prevention control method according to the invention of claim 4 calculates the thickness of the hydrate layer 26 from the pressure difference of the hydrate slurry 68 at the inlet and outlet of the heat exchanger 30, and the hydrate. Control is performed based on the thickness of the layer 26 and the block pattern map 39.

  The heat exchanger blockage prevention control method according to the invention of claim 5 detects blockage of a bypass pipe that is narrower than the transfer pipe provided in the slurry transport ship 37 that is a transfer pipe that transfers the hydrate slurry 68, Control is performed based on the blockage of the bypass pipe and the blockage pattern map 39.

  The heat exchanger blockage prevention control method according to the invention of claim 6 calculates the overall heat transfer coefficient from the temperature and flow rate of the hydrate slurry and refrigerant 28 (brine) at the inlet and outlet of the heat exchanger 30; The thickness of the hydrate layer 26 formed in the heat exchanger 30 is calculated from the decrease in the overall heat transfer coefficient associated with the operation of the heat exchanger 30, and the control is performed based on the thickness of the hydrate layer 26. It is characterized by performing.

  The heat exchanger blockage prevention control method according to the invention of claim 7 is based on the pressure difference of the hydrate slurry at the inlet (hydrate slurry inlet 31) and outlet (hydrate slurry outlet 32) of the heat exchanger 30. The thickness of the hydrate layer 26 formed in the heat exchanger 30 is calculated, and control is performed based on the thickness of the hydrate layer 26.

  Conventionally, the operating conditions under which the blockage of the heat exchanger 30 does not occur in the hydrate manufacturing process have not been clarified, and the operation has been performed by a method of handling when the blockage occurs. As a result, the operating conditions under which the heat exchanger 30 is clogged are clarified, and the creation of the clogging pattern map 39 is realized, thereby making it possible to provide an operation method for preventing clogging in advance.

  It has been clarified that the blockage of the heat exchanger 30 is governed by the Reynolds number of the hydrate slurry 68 that is the object to be cooled and the supercooling temperature from the three-phase equilibrium condition. By mapping the above, it becomes possible to select the operating conditions of the heat exchanger 30 where no blockage occurs, and the continuous operation of the heat exchanger 30 is made possible.

  The block pattern pattern 39 is preferably created by performing a block test on an actual machine and mapping it from the data, but it is also possible to create the block pattern map 39 of the actual machine from the data of the block experiment on the experimental machine. It is also possible to correct the block pattern pattern 39 to be more accurate than the data acquired when operating the actual machine based on the block pattern pattern 39.

  By calculating the thickness of the hydrate layer 26 that causes the blockage generated in the heat exchanger 30 from the change in the overall heat transfer coefficient in the heat exchanger 30, the detailed situation in the heat exchanger 30 is calculated. It is possible to detect the obstruction sign 40 as a possibility of obstruction before the heat exchanger 30 is obstructed. Therefore, when the obstruction sign 40 is detected, the obstruction pattern is detected. Based on the map 39, the operation was changed so that the operation conditions were less likely to cause blockage, thereby realizing continuous operation of the heat exchanger 30.

  Moreover, since the operating condition in which the blockage of the heat exchanger 30 is less likely to occur, that is, the cooling efficiency of the hydrate slurry 68 is low, it is desirable to perform continuous operation under the operation condition immediately before the blockage occurs. By controlling the heat exchanger 30 by combining the sign 40 and the blockage pattern map 39, it is possible to realize continuous operation under the most efficient operation conditions.

  The obstruction sign 40 can be calculated from the pressure difference of the hydrate slurry 68 at the inlet and outlet of the heat exchanger 30 and is expected to have the same effect as when the change in the overall heat transfer coefficient is used. it can.

  Further, it is possible to detect a sign 40 of blockage by installing a bypass pipe thinner than the pipe for transporting the hydrate slurry 68 in the heat exchanger 30 and monitoring the blockage of the bypass pipe. The continuous operation of the heat exchanger 30 can be controlled by the apparatus and control.

  As described above, due to the change in the overall heat transfer coefficient from the heat exchanger 30, the pressure difference of the hydrate slurry 68 that is the object to be cooled, and the clogging of the bypass pipe, the sign 40 of the clogging is generated before the heat exchanger 30 clogs. When this is detected and the sign 40 of the blockage is detected, the operation of the heat exchanger 30 is controlled based on the blockage pattern map 39 to perform continuous operation of the heat exchanger 30.

  Further, the continuous operation of the heat exchanger 30 prevents energy waste due to the clogging release operation, and enables the operation in a condition where the cooling efficiency of the heat exchanger 30 is the highest and no clogging occurs. Reduced the generation cost of.

  Hereinafter, the present invention will be described in detail with reference to embodiments shown in letters.

  FIG. 4 shows a block pattern map 39 used in the control method for preventing blockage of the heat exchanger of the present invention. The subcooling temperature from the three-phase equilibrium condition of the object to be cooled, such as gas hydrate, and the heat exchanger 30 are shown. The relationship of the Reynolds number of the to-be-cooled object is shown. This clogging pattern map 39 is obtained from a clogging experiment for confirming the clogging in the heat exchanger 30 while changing the flow rate and the cooling temperature while keeping the slurry concentration, pressure, and liquid temperature of the object to be cooled constant. .

  The blockage experiment is preferably performed using the heat exchanger 30 that is actually used in a gas hydrate production plant or the like, but the blockage pattern map 39 can also be created using an experimental apparatus. In this case, the heat exchanger 30 is operated in a plant or the like using the block pattern map 39 based on the data obtained from the experimental apparatus. In this operation process, further data on the block state is accumulated. Therefore, it is desirable to correct the block pattern pattern 39.

  The graph of FIG. 4 shows a natural gas hydrate manufacturing plant in which a hydrate slurry transport pipe 37 in the heat exchanger 30 has a 19 mm inner diameter, a pressure of 5 MPa, a temperature of about 6 ° C., and a hydrate concentration in the pipe. The hydrate slurry 68 having a concentration of about 10% was introduced, and the temperature of the refrigerant such as ethylene glycol and the flow rate of the hydrate slurry 68 were changed to obtain an experiment.

Here, the Reynolds number is defined by (V · D) / ν, V is the flow velocity in the pipe [m / s], D is the pipe inner diameter [m], and ν is the slurry kinematic viscosity coefficient [m ² / S]. Moreover, since the equilibrium temperature is about 6 ° C. when the pressure is about 5 MPa, the natural gas hydrate is generated under the condition that the supercooling temperature shown in the graph indicates how low the refrigerant is circulated from this 6 ° C. The shaded area is a condition area where operation is not possible and a blockage occurs.

  FIG. 5 shows a cross section of a hydrate slurry transport pipe 37 that conveys an object to be cooled by the heat exchanger 30. The brine transport pipe 29 and the hydrate slurry transport pipe 37 form a double pipe, and the hydrate The slurry is cooled while being transported on the center side, and the refrigerant (brine) 28 is configured to circulate on the outer peripheral side, and the hydrate layer 26 is formed, but the Reynolds number exceeds 2000 and the turbulent flow is shown. The resulting hydrate slurry 68 destroys the hydrate layer 26, so that the operating range increases as the flow velocity increases, that is, the Reynolds number increases. This can be said to be a self-cleaning effect due to turbulence.

  A general heat exchanger 30 in a natural gas hydrate production plant is operated with the hydrate slurry transport pipe 37 having an inner diameter of 10 mm to 100 mm and a refrigerant temperature of about 1 ° C.

  The operating condition of the above heat exchanger is that the refrigerant of 1 ° C. is circulated with respect to the natural gas hydrate slurry having an equilibrium temperature of 6 ° C., so that the supercooling temperature is 5 ° C. In order not to block, it is understood that it is necessary to operate the heat exchanger 30 under the condition that the Reynolds number exceeds 6000. As a result of actually operating the heat exchanger 30 with the Reynolds number 6000 based on the blocking pattern map 39, Stable operation was possible without blockage.

  When considering the optimum operating conditions based on the blockage pattern map 39, reducing the refrigerant temperature as much as possible increases the cooling efficiency, and this is a large temperature gradient, which is the temperature difference between the hydrate slurry 68 and the refrigerant. This is because the heat transfer speed is increased and the condition that the blockage does not occur is the condition. Therefore, the heat exchanger 30 is operated on the operable region of the blockage pattern map 39 where the supercooling temperature is as high as possible. It turns out that it becomes high efficiency.

  The shape of the clogging pattern map 39 varies depending on the concentration, pressure, liquid temperature, etc. of the slurry to be cooled or the heat exchanger 30, but can be obtained by clogging experiments with actual machines or experimental machines. The pattern map 39 not only realizes continuous operation control in a region where the heat exchanger 30 does not clog, but also makes it possible to obtain an operation condition that allows continuous operation and has the highest cooling efficiency.

  That is, low-cost and high-efficiency operation of the heat exchanger 30 was realized, and high efficiency of gas hydrate production was also realized.

  FIG. 3 shows a circulation system of gas hydrate slurry and refrigerant.

  For example, a gas hydrate is obtained by supplying a gas such as natural gas and a liquid such as water, which are hydrate raw materials, to the hydrate production tank 44. Since generated heat is generated when the gas hydrate is generated, the hydrate slurry 68 generated to remove the generated heat is sent to the heat exchanger 30 for cooling by the slurry pump 43. The hydrate slurry 68 is cooled while being circulated through the hydrate slurry circulation line 45, and the sherbet-like hydrate produced in the hydrate production tank 44 is sent to a hydrate processing step (not shown).

  The refrigerant circulating in the heat exchanger 30 is cooled to a predetermined temperature in the low-temperature thermostatic chamber 42, and is circulated through the refrigerant circulation line 46 by the pump 51.

  Further, in order to control the circulation of the hydrate slurry and the refrigerant, a flow meter 36 is installed in each circulation line, a thermometer 35 is installed in the low-temperature thermostatic bath 42, and the obtained measured values are stored in a computer or the like. It is configured to transmit to the control device 41. The control device 41 grasps the current operating conditions from the obtained measured values, and when the blockage or the like is likely to occur, the flow rate of the slurry pump 43 and the pump 51 is changed, or the temperature of the low temperature thermostat 42 is changed. These circulatory systems are controlled by transmitting signals.

  Specifically, when it is determined by the input signal 47 to the control device 41 that the heat exchanger 30 is clogged or occurs, an output signal 48 for increasing the flow rate of the slurry pump 43 from the control device 41, a low temperature thermostatic chamber By outputting an output signal 48 for increasing the temperature of 42 and an output signal 48 for decreasing the flow rate of the pump 51 in the refrigerant circulation system, the operation condition is controlled to shift to the operable region in the blockage pattern map 39.

  The heat exchanger 30 is operated based on the blockage pattern map 39 obtained by experimenting the experimental machine or the actual machine. For example, when the data obtained by the experimental machine has an error from the actual operation time, When the operation condition is changed due to deterioration of the apparatus such as the heat exchanger 30, the correction of the closing pattern map 39 is required.

  However, it is very inefficient to correct the blocking pattern map 39 by causing the actual machine that has already been incorporated into the plant or the like and has started manufacturing hydrate to be blocked, and cannot be executed.

  Therefore, in the present invention, by analyzing data obtained from various measuring devices installed in the heat exchanger 30 described below, the measured value is input to the control device 41 as a sign 40 of blockage, and control is performed. By accumulating the operating conditions immediately before the blockage without causing the blockage of the heat exchanger 30, the blockage pattern map 39 can be corrected.

  The sign 40 of the blockage is to estimate the thickness of the hydrate layer 26 formed in the hydrate slurry transport pipe 37 shown in FIG. 5 in the heat exchanger 30. By observing details, it is possible to detect the operating conditions immediately before the blockage occurs. By inputting the thickness of the hydrate layer 26 to the control device 41, the heat exchanger 30 can be controlled under the operating conditions with the highest cooling efficiency without blocking the heat exchanger 30.

  Furthermore, the sign 40 of the blockage can be used even in the initial stage of creating the blockage pattern map 39, and it is possible to obtain the operating conditions immediately before the blockage without blocking the experimental machine or the actual machine. Can be done very easily.

  Hereinafter, a method for estimating the thickness of the hydrate layer 26 that is the sign 40 of the blockage will be described. FIG. 1 shows a state in which a measuring device necessary for estimating the thickness of the hydrate layer 26 is installed in the heat exchanger 30.

  The heat exchanger 30 is configured so that the refrigerant flows and cools around the hydrate slurry transport pipe 37, and thermometers 35 are installed at the hydrate slurry inlet 31 and the hydrate outlet 32, respectively. A flow meter 36 such as a Coriolis mass flow meter for measuring the flow rate is installed. In the refrigerant circulation system, thermometers 35 are installed at the refrigerant inlet 33 and the refrigerant outlet 34, respectively, and a flow meter 36 for measuring the flow rate of the refrigerant is installed. A procedure for calculating the thickness of the hydrate layer 26 based on the value obtained from the measuring device will be described below.

First, the amount of heat transfer is calculated by the following formula 1. Where ΔQ is the amount of heat transfer, m [kg / Hr] is the mass flow rate of the hydrate slurry, Cp [kcal / kg · ° C.] is the constant pressure specific heat, Δt [° C.] is the temperature difference between the input and output of the hydrate slurry. Show. These values are given by m for the hydrate slurry flowmeter, Δt by the hydrate inlet and outlet thermometers, and Cp is known because it uses the water value.

Based on the heat transfer amount ΔQ calculated as described above, the overall heat transfer coefficient U is calculated from Equation 2 below. Here, A [m ² ] represents the heat transfer area of the heat exchanger, and Δt [° C.] represents the logarithmic average temperature difference obtained from the hydrate slurry and the refrigerant temperature by the following Equation 3. These values are known from A and determined from the shape of the heat exchanger 30, ΔT0 [° C.] indicates the temperature difference between the refrigerant in / out, and ΔT1 [° C.] indicates the temperature difference in the hydrate slurry in / out. Provided by the thermometer 35.

Finally, the thickness of the hydrate layer 26 is calculated by the following equation 4 based on the overall heat transfer coefficient U obtained by the above equation 2. Here, 1 / U _i [hr · m ² · ° C./kcal] is the thermal resistance when hydrate is generated, and 1 / U _{i, 0} [hr · m ² · ° C./kcal] is before the hydrate is generated. Thermal resistance, λ _h [hr · m ² · ° C./kcal] is the thermal conductivity of the hydrate, d _i [m] is the inner diameter of the hydrate slurry transport pipe 37, and s [m] is the thickness of the hydrate layer Is shown. In these values, λh is a physical property value obtained by an experiment using hydrate. In the present invention, λh = 0.43. 1 / U _{i, 0} is the thermal resistance obtained in the initial operation state of the heat exchanger 30, and 1 / U _i is a value that varies with the formation of the hydrate layer 26 during operation of the heat exchanger 30.

  With the above calculation, the thickness s of the hydrate layer 26 can be obtained, and the thickness of the hydrate layer 26 is input to the control device 41 as a sign 40 of blockage.

  FIG. 3 is a system diagram in which a temperature output signal 47 output from each thermometer 35 installed in the heat exchanger 30 shown in FIG. Show.

Hereinafter, a method different from the above method for estimating the thickness of the hydrate layer 26 which is a sign 40 of occlusion will be described. FIG. 2 shows a state in which a measuring device necessary for estimating the thickness of the hydrate layer 26 is installed in the heat exchanger 30, and the differential pressure between the inlet and outlet of the hydrate slurry transport pipe 37 is shown. A differential pressure gauge 38 for measuring is installed. Based on the value obtained from the measuring device, the thickness of the hydrate layer 26 is calculated by the following formula 5. Here, s (m) is the thickness of the hydrate layer, p ₀ [Pa] of hydrate formation before the pressure difference, p _h [Pa] is the pressure difference at the time of hydrate formation, d _i (m) Hyde The pipe inner diameter of the rate slurry transport pipe 37 is shown. These values p ₀ and p _h is measured by the differential pressure gauge 38, d _i is obtained as the shape of the heat exchanger 30 is known.

  With the above calculation, the thickness s of the hydrate layer 26 can be obtained, and the thickness of the hydrate layer 26 is input to the control device 41 as a sign 40 of blockage.

  FIG. 9 is a system diagram in which the differential pressure output signal 47 output from the differential pressure gauge 38 installed in the heat exchanger 30 shown in FIG. Show.

  The hydrate slurry transport pipe 37 in the heat exchanger 30 is provided with a bypass pipe that is easily blocked, and is configured to detect the blockage of the bypass pipe with a flow meter or the like. It transmits to the control apparatus 41. The operation can be performed without blocking the heat exchanger 30 using the bypass pipe.

  It is desirable that the bypass pipe has a non-operable area that slightly overlaps the operable area of the blockage pattern map 39 of the target heat exchanger 30.

  Further, since the bypass pipe can be easily installed, it can be used in combination with the method for estimating the thickness of the hydrate layer 26 described above. In particular, the bypass pipe is used in an experiment when creating a block pattern pattern, so that when the block of the bypass pipe is detected, the change amount of the operating condition of the heat exchanger 30 is reduced, and the operation range is impossible. It becomes possible to accurately detect the boundary of the region. That is, in an experiment for creating a blockage pattern map without installing the bypass pipe, even if it is in the operable region, the experiment may be performed while finely chopping the change amount of the operating condition more than necessary, and the efficiency may be reduced. Sex is conceivable.

  As described above, according to the heat exchanger blockage prevention control method of the present invention, the operation condition and the control method are provided that do not block the heat exchanger 30 and have high cooling efficiency. Thus, provision of a highly efficient continuous operation control method for the heat exchanger 30 was realized.

  Moreover, in order to improve the efficiency of the heat exchanger 30, the manufacturing cost in the gas hydrate manufacturing process was reduced, and the manufacturing efficiency was improved.

It is the schematic of the heat exchanger comprised so that an overall heat transfer coefficient might be obtained. It is the schematic of the heat exchanger comprised so that a pressure difference could be obtained. It is the systematic diagram which showed one of the Examples of this invention. It is an obstruction | occlusion pattern map of this invention. It is sectional drawing of the pipe | tube in a heat exchanger. It is the conventional systematic diagram using two heat exchangers. It is a systematic diagram which shows the circulation of the refrigerant | coolant of a heat exchanger. It is a systematic diagram of the hydrate slurry manufacturing apparatus. It is the systematic diagram which showed one of the Examples of this invention.

Explanation of symbols

26 Hydrate Layer 30 Heat Exchanger 35 Thermometer 36 Flow Meter 37 Hydrate Slurry Transport Pipe 38 Differential Pressure Gauge 39 Blocking Pattern Map 40 Prediction of Blocking 41 Controller 42 Low Temperature Thermostatic Tank 44 Hydrate Generation Tank 45 Hydrate Slurry Circulation Line 46 Refrigerant circulation line 68 Hydrate slurry

Claims (7)

  In the heat exchanger that cools the hydrate slurry, a block pattern map that indicates the presence or absence of blockage of the heat exchanger is obtained in advance using the Reynolds number and the degree of supercooling from the three-phase parallel condition as parameters. The heat exchanger blockage prevention control method characterized by performing control on the conditions which blockage does not generate | occur | produce.   A heat exchanger that cools a liquid phase in a gas hydrate manufacturing process and is a control method that prevents clogging of a heat exchanger due to generation and adhesion of a hydrate slurry that is an object to be cooled, and is controlled using the clogging pattern map The heat exchanger blockage prevention control method according to claim 1, wherein:   An overall heat transfer coefficient is calculated from the temperature and flow rate of the hydrate slurry and refrigerant at the inlet and outlet of the heat exchanger, and the overall heat transfer coefficient is reduced due to the operation of the heat exchanger. The heat exchanger blockage prevention according to claim 1 or 2, wherein the thickness of the formed hydrate layer is calculated, and control is performed based on the thickness of the hydrate layer and the blockage pattern map. Control method.   The hydrate layer thickness is calculated from the pressure difference of the hydrate slurry at the inlet and outlet of the heat exchanger, and control is performed based on the hydrate layer thickness and the blockage pattern map. The heat exchanger blockage prevention control method according to claim 1 or 2.   The block according to claim 1 or 2, wherein the blockage of the bypass pipe thinner than the transfer pipe provided in the transfer pipe for transferring the hydrate slurry is detected, and the control is performed based on the blockage of the bypass pipe and the blockage pattern map. The heat exchanger blockage prevention control method according to claim 2.   The overall heat transfer coefficient is calculated from the temperature and flow rate of the hydrate slurry and refrigerant at the inlet and outlet of the heat exchanger, and formed in the heat exchanger from the decrease in the overall heat transfer coefficient accompanying the operation of the heat exchanger. The heat exchanger blockage prevention method characterized by calculating the thickness of the hydrate layer and controlling based on the thickness of the hydrate layer.   The thickness of the hydrate layer formed in the heat exchanger is calculated from the pressure difference of the hydrate slurry at the inlet and outlet of the heat exchanger, and control is performed based on the thickness of the hydrate layer. A feature of the heat exchanger blockage prevention method.

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