Open circulating water system and method for extending the operation cycle of the open circulating water system

Abstract

The present invention provides an open circulating water system and a method for extending the operation cycle of the open circulating water system. A precooling device and a cooler are connected through a process material circulation pipeline. The precooling device is arranged in front of the cooler according to the circulation direction of the process material. The precooling device cools the process material entering the precooling device so that the temperature of the cooled process material is adapted to the upper water temperature of the circulating water of the cooler, and the cooled process material is transported to the cooler through the process material circulation pipeline for further cooling, so that the temperature of the process material entering the precooling device and transmitted to the heat transfer pipe is close to the temperature of the circulating water, thereby avoiding the formation of "micro-evaporation" on the wall of the heat transfer pipe, thereby extending the operation cycle of the open circulating water system.

Description

Technical Field

[0001] The invention relates to the technical field of industrial cooling circulating water energy saving, and in particular to an open circulating water system and a method for extending the operating period of the open circulating water system. Background Art

[0002] The petrochemical, chemical, coal chemical and other industries generally use open circulating water systems. The circulating water system is an important public project in various chemical industries. Its operation consumes a lot of water and electricity. The circulating cooling water replenishment of coal chemical enterprises accounts for about 60% of the total water intake of the whole plant, and the power consumption of the circulating water system accounts for about 8%-10% of the total electricity consumption of the enterprise.

[0003] The circulating water systems of most enterprises have the problem of high energy consumption due to factors such as large design surplus, mismatch with device transformation, low equipment efficiency, and unreasonable operation. In response to the above problems, the existing circulating water energy-saving system optimization and transformation technology mainly focuses on the circulating water pump, but pays little attention to the cooling medium of the production equipment. Pay attention to the patent technology of circulating water coolers, such as the Chinese invention patent with publication number CN103984999A. Although it involves the cooling equipment of the device, it does not mention the heat utilization of the production device and how to effectively adjust the operation of the circulating water system when the device changes in load or season.

[0004] The Chinese invention patent with patent application number CN202010943599.8 and name "Optimization method of industrial circulating water energy-saving system and industrial circulating water energy-saving system using the same" has the following specific scheme: after statistical analysis of the circulating water pump, cooling tower and process device heat exchanger of the circulating water system, the heat exchanger of the entire circulating water system is divided into a high-zone heat exchanger part located in the high-position area and a low-zone heat exchanger part located in the low-position area according to the height position of the heat exchanger of each process device. A model is built through fluid simulation calculation software to perform circulating water flow balance and system head calculation simulation analysis. Then, the economic benefit is evaluated in combination with the operating costs and construction investment costs, and the dividing line between the high-zone heat exchanger part and the low-zone heat exchanger part with the best economic benefits is reasonably selected. The invention mainly achieves the maximum energy saving of the circulating water system by reducing the head of the pump. In the prior art, most of the gas phase at the top of the distillation tower is condensed and cooled by the cooler. The heat of the condensation process is very large, resulting in a large water consumption of the circulating water system and a high water consumption for replenishment. In addition, due to the large membrane heat transfer coefficient of the condensation process, the wall temperature of the heat transfer tube in the cooler is close to the condensation temperature of the process material. The water pressure of the circulating water system is generally low, especially for the high-level cooler. Generally, the outlet pressure of the high-level cooler is slightly higher than the normal pressure. In this case, when the circulating water contacts the high-temperature tube wall in the cooler, it is easy to form "micro-evaporation" on the heat transfer tube wall, and it is very easy to fold out the calcium, magnesium, etc. in the circulating water, thereby causing hard scale to appear on the heat transfer tube wall due to crystallization. As the operating time increases, the hard scale will become thicker and thicker, the flow area on the circulating water side of the heat exchanger will decrease, and the outlet water temperature will increase, which will further aggravate the "micro-evaporation", resulting in the temperature of the process material after cooling failing to meet the requirements, resulting in the relatively short operating cycle of the open circulating water system. Summary of the invention

[0005] In view of this, the present invention provides an open circulating water system to solve the problem in the prior art that the cooler in the open circulating water system is prone to scaling of the heat transfer tube wall of the cooler due to high operating load, thereby shortening the operating cycle.

[0006] The invention also provides a method for extending the operation period of an open circulating water system.

[0007] An open circulating water system includes a pre-cooling device and a cooler, which are connected through a process material circulation pipeline. The pre-cooling device is arranged in front of the cooler according to the circulation direction of the process material. The pre-cooling device cools the process material entering the pre-cooling device so that the temperature of the cooled process material matches the circulating water temperature of the cooler, and the cooled process material is transported to the cooler through the process material circulation pipeline for further cooling.

[0008] Preferably, the above-mentioned cooler is also provided with a discharge pipe for process materials, a circulating water inlet pipe and a circulating water discharge pipe. The open circulating water system also includes a control component, which is used to control the operating power of the pre-cooling equipment so that the temperature of the process material entering the cooler reaches a predetermined value. The control component includes a controller, a first temperature transmitter for collecting the temperature of the process material before entering the cooler, a second temperature transmitter for collecting the temperature of the process material flowing out of the cooler, and a third temperature transmitter for collecting the temperature of the circulating water flowing out of the cooler. The controller is electrically connected to the first temperature transmitter, the second temperature transmitter, and the third temperature transmitter respectively. The first temperature transmitter is arranged on the inlet pipe before the process material enters the cooler, the second temperature transmitter is arranged on the discharge pipe after the process material flows out of the cooler, and the third temperature transmitter is arranged on the circulating water discharge pipe. The controller adjusts the heat exchange efficiency of the pre-cooling equipment according to the temperature numerical signal collected by the first temperature transmitter, the temperature numerical signal collected by the second temperature transmitter, and the temperature numerical signal collected by the third temperature transmitter.

[0009] Preferably, the pre-cooling device is a heat medium water heat exchanger, the heat medium water heat exchanger is provided with a heat medium water circulation pipeline and a heat medium water circulation pump, and the heat medium water circulation pump and the controller are electrically connected.

[0010] Preferably, the pre-cooling device is an air cooler, and the fan and controller of the air cooler are electrically connected.

[0011] Preferably, the pre-cooling equipment is formed by connecting a heat medium water heat exchanger and an air cooler in series through a process material conveying pipeline, the air cooler is located between the heat medium water heat exchanger and the cooler, the heat medium water heat exchanger is provided with a heat medium water circulation pipeline and a heat medium water circulation pump, the heat medium water circulation pump and the controller are electrically connected, and the fan of the air cooler and the controller are electrically connected.

[0012] An optimization method for extending the operation cycle of an open circulating water system, the method is applied to an open circulating water system including a pre-cooling device, a cooler and a control component, and the specific steps of the method are:

[0013] S1. First, the process material of the production device is cooled by pre-cooling equipment, and then the cooled process material is input into the cooler for cooling, so that the temperature of the cooled process material is compatible with the circulating water temperature of the cooler;

[0014] S2. Model and analyze the circulating water supply pipeline system without cooling equipment, calculate the pressure loss of the pipe network system, set pressure measuring instruments at the inlet and outlet of each of the above coolers, and perform real-time pressure measurement. Among all the above pressure measurement data, find the three coolers with the lowest pressure, and mark the cooler with the lowest outlet pressure as the key line, the cooler with the second lowest outlet pressure as the sub-key line, and the other cooler as the attention line. Add pressure transmitters at the outlets of the three coolers marked as the key line, sub-key line, and attention line, respectively, to monitor the outlet pressure values ​​of the three coolers in real time;

[0015] S3. Optimization of cooling process of coolers with start-up coolers or one-on-one standby equipment: For equipment with start-up coolers, they are designed in a switchable manner in series and parallel with coolers for low-level non-critical logistics. That is, they are put into use in parallel when the equipment is started. After the production equipment is running normally, they are switched to series mode, and the circulating water first enters the start-up cooler and then flows through the cooler for non-critical logistics; for coolers with one-on-one standby equipment, the two water-using equipment are set in a switchable manner in series and parallel. When the standby cooler needs to be started, it is switched to parallel mode, and both coolers use water. When the equipment is running normally and the start-up cooler stops running, it is switched to series mode, and the circulating water flows through the two coolers in sequence.

[0016] S4. Reasonable water consumption and real-time water consumption operation adjustment method of coolers: According to the reasonable water consumption of each cooler, the reasonable water consumption of each production unit is obtained, and then the reasonable water consumption of the entire circulating water system is obtained.

[0017] S41. Reasonable water consumption and reasonable flow rate of a single cooling device: The temperature of the reasonable water consumption of a single cooling device should meet the post-cooling temperature of the process material and the requirements of the process card or production operation. It can be calculated using heat transfer calculation software or judged based on the actual operation conditions on site; the temperature of the cooling water out of the cooler is less than or equal to 55°C;

[0018] Reasonable flow rate of circulating water: When circulating water flows through the tube side, the flow rate of circulating water is 0.5m / s or above; when circulating water flows through the shell side, the flow rate of circulating water is 0.3m / s or above, and it is greater than 0.20m / s when anti-corrosion coatings or backwashing measures are taken; for the circulating water pipe side equipment that has been put into use, if the flow rate of circulating water cannot meet 0.5m / s or above, it can be achieved by blocking some heat exchange tubes; when pre-cooling equipment or pre-air cooler is set, the outlet temperature of process materials of the pre-cooling equipment or air cooler should be adjusted, and the flow rate of circulating water in the cooler should reach the above reasonable flow rate;

[0019] S42. Adjustment of reasonable water volume and reasonable flow rate for cooling equipment with particularly large design margins: For water cooling equipment with particularly large design margins, some coolers shall be removed (not put into use) so that the flow rate of circulating water in the cooling equipment reaches a reasonable flow rate greater than 0.5m / s (circulating water pipe flow) while meeting the cooling requirements of process materials. When circulating water is flowing through the pipe flow, the reasonable flow rate is achieved by partially blocking the pipe and reducing the flow area of ​​the pipe flow;

[0020] S43. Calculation method of real-time water consumption of a single cooling device: Based on process logistics and physical properties, the real-time data of the operating pressure, inlet temperature and outlet temperature of the process logistics are measured on the production device. A remote (local) thermometer is installed on the circulating water outlet pipeline of each cooler. Then we can use:

[0021] W = CP (logistics) × ΔT1 (logistics) / ΔT2 (circulating water)

[0022] Where: W: is the consumption of circulating water

[0023] CP (logistics): is the average specific heat capacity of process logistics

[0024] ΔT1 (logistics): cooling temperature difference of process logistics, inlet temperature minus outlet temperature

[0025] ΔT2 (circulating water): The temperature difference between the upper and lower water of the circulating water, the outlet temperature minus the inlet temperature

[0026] CP (logistics) × ΔT1 (logistics): total cooling heat load of process materials in the cooler

[0027] S44. Real-time monitoring and operation of water consumption: Based on the comparison of the reasonable water consumption of each cooler with the real-time water consumption measured by soft measurement, if the deviation between the real-time water consumption and the reasonable water consumption is within ±10%, it is in good operation; if the deviation between the real-time water consumption and the reasonable water consumption is +10~20%, it means that the circulating water consumption is too much, and -10~20% means that the circulating water consumption is too little; if the deviation between the real-time water consumption and the reasonable water consumption is >20%, it means that the circulating water consumption is seriously too much, and <-20% means that the circulating water consumption is seriously too little; the operator shall make corresponding adjustments to the water consumption of the cooler based on the above judgment method of whether the water consumption is reasonable;

[0028] S45, full parallel system water supply pressure and water supply pressure real-time adjustment method:

[0029] When designing and selecting the circulating pump, the pressure that meets the water supply needs of the key lines in summer and under the condition of maximum processing volume should be selected, and an appropriate margin should be left; during the normal production process of the circulating water system, the theoretical calculated pressure loss of the pipeline should be compared with the measured pressure loss in real time; according to the real-time measurement values ​​of the pressure transmitters on the key lines, sub-key lines, and concerned lines, they should be associated with the circulating water pump to adjust the opening of the circulating water pump outlet valve;

[0030] S46. For a system with a cooler that is arranged at a particularly high position or has a particularly large pressure loss, a booster pump needs to be added; a booster pump is added to the circulating water main pipe to increase the inlet pressure of the circulating water of the cooler, and the head of the booster pump is selected to ensure that the outlet pressure of the cooler is greater than zero; before the return water pipe of the cooler returns to the main pipe, a valve needs to be installed to reduce the pressure, and the pressure reduced by the valve is equivalent to the head of the booster pump to avoid increasing the total main pipe pressure after the return water of the cooler;

[0031] S47. Operation optimization of circulating water pumps: The pumps of the circulating water system are all parallel systems. According to the operating characteristics of parallel pumps, the flow rate of a single circulating water pump is selected based on the principle that the actual number of pumps running in parallel should not exceed 4. The number of running pumps is N, and N-1 pumps should operate in the optimal efficiency zone of the pump. The Nth pump is used as a backup pump. When the actual efficiency of a pump is found to be low, the backup pump is started to check the use of the impeller of the pump with low actual efficiency.

[0032] Preferably, in step S1, "reducing the cooling load of the cooler" specifically includes setting a pre-cooling device on the process material entry side of the cooler to recover the heat of the process material before entering the cooler, thereby reducing the total cooling load of the cooler.

[0033] Preferably, a temperature transmitter is provided on the process material discharge side of the precooling equipment, and the outlet temperature of the process material is determined according to the properties of the process material and the cooling medium used by the precooling equipment. The properties of the process material are non-toxic, non-harmful, non-severely corrosive, and non-abrasive fluid substances. When the cooling medium is pure liquid phase cooling, the temperature of the process material flowing out of the precooling equipment is 75°C-100°C; or when the cooling medium is pure component condensation, the temperature of the process material flowing out of the precooling equipment is less than the condensation temperature of the cooling medium, and the temperature of the process material flowing out of the precooling equipment is 75°C-100°C; or when the cooling medium is multi-component condensation, the temperature of the process material flowing out of the precooling equipment is less than 70-80% of the condensation temperature of the process material, and the temperature of the process material flowing out of the precooling equipment is 75°C-100°C.

[0034] Preferably, "pre-cooling equipment is arranged on the process material entry side of the cooler to recover the heat of the process material before entering the cooler, thereby reducing the total cooling load of the cooler" specifically means: the fractionation tower adopts direct heat pump, indirect heat pump, or tower heat coupling to reduce the temperature of the process material entering the cooler, thereby reducing the total cooling load;

[0035] For the overhead product of a fractionation tower such as a liquefied petroleum gas separation tower, where the temperature difference between the top and bottom is less than 20°C and there is basically no non-condensable gas, a compressor can be used to pressurize the overhead product to increase the temperature of the overhead product, and then the bottom product can be used as a heat source for the reboiler of the tower or other coupled towers;

[0036] If the distillate from the top of the tower contains non-condensable gas or corrosive media, an indirect heat pump can be used to recover heat and reduce the cooling load;

[0037] When multiple distillation towers are operated in series, when the steam tower temperature of the front tower is 20°C or more higher than the bottom temperature of the rear tower, the top steam of the front tower can provide all or most of the energy for the rear tower. The two towers are thermally coupled to reduce the heat source consumption of the low reboiler of the rear tower and the condensation load of the top gas phase of the front tower.

[0038] Preferably, in step S1, "reducing the cooling load of the cooler" specifically includes: setting an air cooler on the water inlet side of the cooler to reduce the temperature of the process material entering the cooler, thereby reducing the total cooling load of the cooler.

[0039] Preferably, a temperature transmitter is provided on the water outlet side of the air cooler, and the outlet temperature of the process material is determined according to the properties of the process material and the cooling medium used by the pre-cooling equipment. The properties of the process material are non-toxic, non-harmful, non-severely corrosive, and non-abrasive fluid substances. When the cooling medium is pure liquid phase cooling, the temperature of the process material flowing out of the air cooler is 65°C-70°C; or when the cooling medium is pure component condensation, the temperature of the process material flowing out of the air cooler is 65°C-70°C; or when the cooling medium is multi-component condensation, the temperature of the process material flowing out of the air cooler is 65°C-70°C.

[0040] Preferably, in step S1, "reducing the cooling load of the cooler" is specifically as follows: a pre-cooling device and an air cooler are sequentially arranged on the process material entrance side of the cooler, the heat of the process material is first recovered by the pre-cooling device, and then the process material with part of the heat recovered is cooled again by the air cooler, and finally the process material is cooled by the cooler to reduce the total cooling load of the cooler.

[0041] In the above-mentioned open circulating water system and the optimization method for extending the operation cycle of the open circulating water system, the pre-cooling equipment and the cooler are connected through the process material circulation pipeline, and the pre-cooling equipment is arranged in front of the cooler according to the flow direction of the process material. The pre-cooling equipment cools the process material entering the pre-cooling equipment so that the temperature of the cooled process material is adapted to the circulating water upper water temperature of the cooler, and the cooled process material is transported to the cooler through the process material circulation pipeline for further cooling, so that the temperature of the entering process material transmitted to the heat transfer tube is close to the temperature of the circulating water, thereby avoiding the formation of "micro-evaporation" on the wall of the heat transfer tube, thereby extending the operation cycle of the open circulating water system. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 It is a structural block diagram of the first embodiment of the present invention.

[0043] Figure 2 It is a structural block diagram of the second embodiment of the present invention.

[0044] Figure 3 It is a structural block diagram of the third embodiment of the present invention.

[0045] Figure 4 This is a structural block diagram of the present invention in which a booster pump is set on a key line after modeling and analyzing the pipeline system.

[0046] In the figure: pre-cooling equipment 10, heat medium water heat exchanger 11, air cooler 12, cooler 20, discharge pipe 22 of process material, circulating water inlet pipe 23, circulating water outlet pipe 24, control component 30, controller 31, first temperature transmitter 32, second temperature transmitter 33, third temperature transmitter 34, air cooler 40. DETAILED DESCRIPTION

[0047] The technical scheme and technical effects of the present invention are further elaborated in detail below in conjunction with the accompanying drawings of the present invention.

[0048] See also Figures 1 to 3 The open circulating water system includes a pre-cooling device 10 and a cooler 20, which are connected via a process material circulation pipeline 30. The initial end of the process material circulation pipeline 30 is connected to a production device, for example, the production device is a distillation tower. The pre-cooling device 10 is arranged in front of the cooler 20 according to the circulation direction of the process material. The pre-cooling device 10 cools the process material entering the pre-cooling device 10 so that the temperature of the cooled process material matches the circulating water upper temperature of the cooler 20, and transports the cooled process material to the cooler 20 through the process material circulation pipeline 30 for further cooling.

[0049] Furthermore, the cooler 20 is also provided with a discharge pipe 22 for process materials, a circulating water inlet pipe 23 and a circulating water outlet pipe 24. The open circulating water system also includes a control component 30. The control component 30 is used to control the operating power of the pre-cooling device 10 so that the temperature of the process material entering the cooler 20 reaches a predetermined value. The control component 30 includes a controller 31, a first temperature transmitter 32 for collecting the temperature of the process material before entering the cooler 20, a second temperature transmitter 33 for collecting the temperature of the process material flowing out of the cooler 20, and a third temperature transmitter 34 for collecting the temperature of the circulating water entering the cooler 20. The controller 31 is electrically connected to the first temperature transmitter 32, the second temperature transmitter 33 and the third temperature transmitter 34 respectively. The first temperature transmitter 32 is arranged at the process material inlet. The second temperature transmitter 33 is arranged on the inlet pipe before entering the cooler 20, the third temperature transmitter 34 is arranged on the circulating water inlet pipe 23, and the controller 31 adjusts the heat exchange efficiency of the pre-cooling equipment 10 on the premise that the real-time temperature of the process material flowing out of the cooler 20 meets the temperature required by the process according to the temperature numerical signal collected by the first temperature transmitter 32, the temperature numerical signal collected by the second temperature transmitter 33 and the temperature numerical signal collected by the third temperature transmitter 34, and changes the temperature difference between the real-time temperature of the process material before entering the cooler 20 and the real-time temperature of the circulating water to reduce the cooling load of the cooler 20, and at the same time reduce the probability of scaling of the heat transfer pipe wall of the cooler 20, so as to achieve the purpose of extending the operation period of the open circulating water system.

[0050] Furthermore, the pre-cooling device 10 is a heat medium water heat exchanger, and the heat medium water heat exchanger is provided with a heat medium water circulation pipeline and a heat medium water circulation pump. The heat medium water circulation pump and the controller 31 are electrically connected. The controller 31 adjusts the speed of the heat medium water circulation pump to adjust the heat exchange efficiency of the heat medium water heat exchanger under the premise that the real-time temperature of the process material flowing out of the cooler 20 meets the temperature required by the process based on the temperature numerical signal collected by the first temperature transmitter 32, the temperature numerical signal collected by the second temperature transmitter 33 and the temperature numerical signal collected by the third temperature transmitter 34.

[0051] Furthermore, the pre-cooling device 10 is an air cooler, and the fan of the air cooler is electrically connected to the controller 31. The controller 31 adjusts the speed of the air cooler fan to adjust the heat exchange efficiency of the air cooler under the premise that the real-time temperature of the process material flowing out of the cooler 20 meets the temperature required by the process, based on the temperature numerical signal collected by the first temperature transmitter 32, the temperature numerical signal collected by the second temperature transmitter 33 and the temperature numerical signal collected by the third temperature transmitter 34.

[0052] Furthermore, the pre-cooling equipment 10 is formed by connecting a heat medium water heat exchanger and an air cooler in series through a process material conveying pipeline. The air cooler is located between the heat medium water heat exchanger and the cooler 20. The heat medium water heat exchanger is provided with a heat medium water circulation pipeline and a heat medium water circulation pump. The heat medium water circulation pump and the controller 31 are electrically connected. The fan of the air cooler and the controller 31 are electrically connected. The controller 31 ensures that the real-time temperature of the process material flowing out of the cooler 20 meets the temperature required by the process based on the temperature numerical signal collected by the first temperature transmitter 32, the temperature numerical signal collected by the second temperature transmitter 33 and the temperature numerical signal collected by the third temperature transmitter 34. The controller 31 adjusts the speed of the heat medium water circulation pump and the speed of the air cooler fan, thereby adjusting the heat exchange efficiency of the heat medium water heat exchanger and the air cooler respectively.

[0053] Furthermore, the present invention also provides an optimization method for extending the operation period of an open circulating water system, which is applied to the above-mentioned open circulating water system including a pre-cooling device, a cooler and a control component, and the specific steps of the method are:

[0054] S1. First, the process material of the production device is cooled by pre-cooling equipment, and then the cooled process material is input into the cooler for cooling, so that the temperature of the cooled process material is compatible with the circulating water temperature of the cooler;

[0055] S2. Model and analyze the circulating water supply pipeline system without cooling equipment, calculate the pressure loss of the pipeline system, set pressure measuring instruments at the inlet / outlet of each of the above-mentioned coolers 20, and perform real-time pressure measurement. Among all the above-mentioned pressure measurement data, find the three coolers 20 with the lowest pressure, and mark the cooler 20 with the lowest outlet pressure as the critical line, the cooler with the second lowest outlet pressure as the sub-critical line, and the other one as the focus line. Pressure transmitters are respectively added to the outlets of the three coolers 20 marked as the critical line, the sub-critical line and the focus line to monitor the outlet pressure values ​​of the three coolers 20 in real time.

[0056] S3. Optimization of cooling process of coolers with startup coolers or one-on-one standby equipment: For equipment with startup coolers, they are designed in a switchable series / parallel mode with the coolers for low-level non-critical logistics, that is, they are put into use in parallel mode when the equipment is started, and after the production equipment is running normally, they are switched to the series mode, and the circulating water first enters the startup cooler and then flows through the cooler for non-critical logistics; when the startup cooler is set in series, under normal production conditions, the flow rate of all circulating water flowing through the cooling equipment is greater than 0.5m / s when the circulating water flows through the pipe side, and greater than 0.3m / s when the circulating water flows through the shell side. If the shell side adopts anti-corrosion coating or backwashing measures, it is greater than 0.20m / s. For the coolers of one-on-one standby equipment, the two water-using equipment are set in a switchable series / parallel mode. When the standby cooler needs to be started, it is switched to the parallel mode, and both coolers use water. When the equipment is running normally and the startup cooler stops running, it is switched to the series mode, and the circulating water flows through the two coolers in sequence. The problem that the water in the start-up cooler does not flow for a long time after the start-up cooler stops running in the prior art and thus the equipment is corroded is avoided, and the operation cycle of the start-up cooler is prolonged.

[0057] S4. Method for adjusting the reasonable water consumption and real-time water consumption of the cooler: According to the reasonable water consumption of each cooler, the reasonable water consumption of each production device is obtained, and then the reasonable water consumption of the entire circulating water system is obtained. This step is specifically as follows:

[0058] S41. Adjustment of reasonable water consumption and reasonable flow rate of a single cooler: The temperature of reasonable water consumption of a single cooler 20 should simultaneously meet the post-cooling temperature of the process material and the requirements of the process card or production operation. It can be calculated using heat transfer calculation software or determined based on actual on-site operation conditions; the temperature of cooling water out of the cooler is less than or equal to 55°C, preferably less than or equal to 50°C.

[0059] Reasonable flow rate of circulating water: when circulating water flows through the tube side, the flow rate of circulating water is 0.5m / s or above; when circulating water flows through the shell side, the flow rate of circulating water is greater than 0.3m / s, and the flow rate of circulating water is greater than 0.20m / s when anti-corrosion coatings or backwashing measures are taken; for the circulating water pipe side equipment that has been put into use, when the flow rate of circulating water cannot be greater than 0.5m / s, it is achieved by blocking some heat exchange tubes; when a pre-cooling device 10 or a pre-air cooler 40 is set, the outlet temperature of the process materials of the pre-cooling device 10 or the air cooler 40 should be adjusted, and the flow rate of circulating water in the cooler should reach the above-mentioned reasonable flow rate.

[0060] S42. Adjustment of reasonable water volume and reasonable flow rate for cooling equipment with particularly large design margins: For water cooling equipment with particularly large design margins, the method of cutting off (not putting into use) some coolers 20 is adopted. While meeting the cooling requirements of process materials, the flow rate of circulating water in the cooling equipment reaches a reasonable flow rate greater than 0.5m / s (circulating water running through the pipe). When the circulating water runs through the pipe, the reasonable flow rate is achieved by partially blocking the pipe and reducing the flow area of ​​the pipe.

[0061] When selecting the cooling equipment of the production unit, especially the top condenser, a 100% or even 300% design margin is always reserved. It is very difficult to achieve a reasonable flow rate for such cooling equipment with a particularly large design margin. During the production process, enterprises generally control the inlet water volume of the circulating water of the cooling equipment according to the outlet temperature of the process materials. This control method results in a higher outlet temperature of the circulating water and a lower flow rate of the circulating water in the cooler. As a result, in the heat exchanger, the sludge in the circulating water is deposited due to the low flow rate, resulting in "soft scale" of sludge deposition in the tube (outside the tube when the circulating water goes through the shell). After a long period of operation, the soft scale gradually hardens, and microorganisms multiply under the scale, resulting in under-scale corrosion, which affects the normal production of the circulating water system and also affects the stable and long-term production of the device. The present invention sets a reasonable water volume for the cooler, which not only takes into account the cooling requirements of the process materials, but also takes into account the outlet temperature of the circulating water and the flow rate of the circulating water in the cooler, thereby avoiding the problems of "soft scale" and under-scale corrosion caused by the deposition of slime-like substances due to too low a flow rate, and solves the contradiction between the long-term safe operation of the equipment and the reduction of the amount of circulating water used.

[0062] S43. Calculation method of real-time water consumption of a single cooler: Based on process logistics and physical properties, the real-time data of the operating pressure, inlet temperature and outlet temperature of the process logistics are measured on the production device. A remote (local) thermometer is installed on the circulating water outlet pipeline of each cooler. Then we can use:

[0063] W=CP(logistics)×ΔT1(logistics) / ΔT2(circulating water)

[0064] Calculate the water consumption of this single cooler.

[0065] Where: W: is the water consumption of a single cooler

[0066] CP (logistics): is the average specific heat capacity of process logistics

[0067] ΔT1 (logistics): cooling temperature difference of process logistics, inlet temperature minus outlet temperature

[0068] ΔT2 (circulating water): The temperature difference between the upper and lower water of the circulating water, the outlet temperature minus the inlet temperature

[0069] CP (logistics) × ΔT1 (logistics): Total cooling heat load of process materials in cooler 20

[0070] Since it is impossible to install a circulating water flow meter on each water cooler in the production equipment, the actual flow rate of the circulating water in the cooler cannot be obtained during the actual production process, so it is impossible to obtain real-time water consumption data for actual production. The water consumption of each cooler is obtained through step S43, and the total water consumption of the circulating water system is calculated based on the sum of the water consumption of each cooler in the circulating water system.

[0071] S44. Real-time monitoring and operation of water consumption: Based on the comparison between the reasonable water consumption of each cooler and the real-time water consumption of soft measurement, if the deviation between the real-time water consumption and the reasonable water consumption is within ±10%, it is in good operation; if the deviation between the real-time water consumption and the reasonable water consumption is +10~20%, it means that the circulating water consumption is too much, and -10~20% means that the circulating water consumption is too little; if the deviation between the real-time water consumption and the reasonable water consumption is >20%, it means that the circulating water consumption is seriously too much, and <-20% means that the circulating water consumption is seriously too little; the operator shall make corresponding adjustments to the water consumption of the cooler based on the above judgment method of whether the water consumption is reasonable.

[0072] S45. Water supply pressure of the full parallel system and real-time adjustment method of water supply pressure: When designing and selecting the circulating pump, the pressure that meets the water supply needs of the key lines in summer and under maximum processing conditions should be selected, and an appropriate margin should be left; during normal production of the circulating water system, the theoretical calculated pressure loss and the measured pressure loss of the pipeline should be compared in real time; based on the real-time measurement values ​​of the pressure transmitters on the key lines, sub-key lines, and attention lines, they should be associated with the circulating water pump to adjust the opening of the circulating water pump outlet valve.

[0073] For example: If the lowest value among the pressure indication values ​​at the outlet of all the highest-position coolers is higher than 0.02Mpa, the pump outlet valve can be closed.

[0074] For example: If the lowest value among the pressure indication values ​​at the outlet of all the highest-position coolers is lower than 0.01Mpa, open the pump outlet valve.

[0075] For example: if the lowest value of the pressure indication values ​​at the outlet of all the highest-level coolers is higher than 0.02Mpa, and closing the pump outlet valve will put the pump operation in a non-efficient area, you can turn off one circulating water pump and make corresponding adjustments to the other water pumps to keep the water supply and pressure at reasonable values.

[0076] For example: if the lowest value of the pressure indication values ​​at the outlet of all the highest-level coolers is lower than 0.01Mpa, and opening the outlet valves of one or several pumps will put the operation of the combined pumps in a non-efficient area, then an additional circulating water pump can be added, and other water pumps can be adjusted accordingly to keep the water supply volume and water supply pressure at reasonable values.

[0077] For example: In a circulating water system equipped with a speed-regulating pump (variable frequency / hydraulic coupling or permanent magnet), closed-loop regulation can also be performed based on the highest pressure measurement results of the key lines.

[0078] S46. For systems with coolers that are located at particularly high locations or have particularly large pressure losses, it is necessary to add a booster pump. Figure 4 ; Add a booster pump to the circulating water main to increase the inlet pressure of the circulating water of the cooler. The head of the booster pump is selected to ensure that the outlet pressure of the cooler is greater than zero; before the return water pipe of the cooler returns to the main pipe, a valve needs to be installed to reduce the pressure. The pressure reduced by the valve is equivalent to the head of the booster pump to avoid increasing the total main pipe pressure after the return water of the cooler.

[0079] If the pressure loss of a cooling device in the circulating water system is particularly large (for example, all coolers have 2 pipe passes, and this cooler has 4 or 6 pipe passes), after using a multi-pass cooler, the pressure loss of the cooler will be greater than that of a 2-pass cooling device. In this case, in order to ensure the normal operation of the cooler, a booster pump needs to be added, and the head of the booster pump is the pressure loss difference between this cooler and most other coolers.

[0080] S47. Operation optimization of circulating water pumps: The pumps of the circulating water system are all parallel systems. According to the operating characteristics of parallel pumps, the flow rate of a single circulating water pump is selected based on the principle that the actual number of pumps running in parallel should not exceed 4. The number of running pumps is N, and N-1 pumps should operate in the optimal efficiency zone of the pump. The Nth pump is used as a backup pump. When the actual efficiency of a pump is found to be low, the backup pump is started to check the use of the impeller of the pump with low actual efficiency.

[0081] The above-mentioned single cooler is any cooler in the circulating water system.

[0082] Furthermore, in step S1, “reducing the cooling load of the cooler” specifically involves setting a pre-cooling device 10 (such as a heat medium water heat exchanger) on the process material entrance side of the cooler 20 to recover the heat of the process material before entering the cooler 20, thereby reducing the total cooling load of the cooler 20.

[0083] Among them, a temperature transmitter is set on the process material discharge side of the precooling device 10, and the outlet temperature of the process material is determined according to the nature of the process material and the cooling medium used by the precooling device 10. The nature of the process material is a non-toxic, non-harmful, non-severely corrosive, and non-abrasive fluid substance. When the cooling medium is pure liquid phase cooling, the temperature of the process material flowing out of the precooling device 10 is 75°C-100°C; or when the cooling medium is pure component condensation, the temperature of the process material flowing out of the precooling device 10 is less than the condensation temperature of the cooling medium, and the temperature of the process material flowing out of the precooling device 10 is 75°C-100°C; or when the cooling medium is multi-component condensation, the temperature of the process material flowing out of the precooling device 10 is less than 70-80% of the condensation temperature of the process material, and the temperature of the process material flowing out of the precooling device 10 is 75°C-100°C. After heat recovery, most of the heat of the process flow is recovered, and the circulating water cooler is used as a supplementary cooler to supplement cooling.

[0084] Furthermore, “pre-cooling equipment is provided on the process material entry side of the cooler to recover the heat of the process material before entering the cooler and reduce the total cooling load of the cooler” specifically means: the fractionation tower adopts direct heat pump, or indirect heat pump, or tower heat coupling, etc. to reduce the temperature of the process material entering the cooler and reduce the total cooling load;

[0085] For the overhead product of a fractionation tower such as a liquefied petroleum gas separation tower, where the temperature difference between the top and bottom is less than 20°C and there is basically no non-condensable gas, a compressor can be used to pressurize the overhead product to increase the temperature of the overhead product, and then the bottom product can be used as a heat source for the reboiler of the tower or other coupled towers;

[0086] If the distillate from the top of the tower contains non-condensable gas or corrosive media, an indirect heat pump can be used to recover heat and reduce the cooling load;

[0087] When multiple distillation towers are operated in series, when the steam tower temperature of the front tower is 20°C or more higher than the bottom temperature of the rear tower, the top steam of the front tower can provide all or most of the energy for the rear tower. The two towers are thermally coupled to reduce the heat source consumption of the low reboiler of the rear tower and the condensation load of the top gas phase of the front tower.

[0088] Furthermore, in other embodiments, "reducing the cooling load of the cooler" in step S1 is specifically to set an air cooler on the water inlet side of the cooler to reduce the temperature of the process material entering the cooler, thereby reducing the total cooling load of the cooler.

[0089] Furthermore, a temperature transmitter is arranged on the outlet side of the air cooler, and the outlet temperature of the process material is determined according to the properties of the process material and the cooling medium used by the pre-cooling equipment. The properties of the process material are non-toxic, non-harmful, non-severely corrosive and non-abrasive fluid substances. When the cooling medium is pure liquid phase cooling, the temperature of the process material flowing out of the air cooler is 65°C-70°C; or when the cooling medium is pure component condensation, the temperature of the process material flowing out of the air cooler is 65°C-70°C; or when the cooling medium is multi-component condensation, the temperature of the process material flowing out of the air cooler is 65°C-70°C.

[0090] Furthermore, in the third embodiment, "reducing the cooling load of the cooler" in step S1 is specifically to sequentially set a pre-cooling device and an air cooler on the process material entrance side of the cooler, first recover the heat of the process material with the pre-cooling device, then use the air cooler to cool the process material with part of the heat recovered again, and finally cool it down through the cooler to reduce the total cooling load of the cooler.

[0091] After the above steps, when the temperature of the process material is high and the cooling load is large before entering the cooler 20, a process material outlet temperature transmitter is added between the pre-cooling equipment 10 and the cooler 20 of the production device. The temperature transmitter measures the temperature in real time and transmits the temperature signal to the control component 30. The control component 30 controls the temperature of the process material outlet side of the pre-cooling equipment 10. On the one hand, the cooling load of the cooler 20 on the high-temperature medium is greatly reduced, the circulation volume of the circulating water is reduced, and the evaporation water volume of the cooling tower is greatly reduced. At the same time, the direct cooling of the high-temperature medium by the cooler 20 in the production device is reduced, and the hard scaling phenomenon caused by the high temperature medium heating the pipe wall of the cooler 20 of the production device to form a high temperature is greatly reduced, thereby extending the operation cycle of the cooler 20 of the production device.

Claims

1. A method for extending the operating period of an open circulating water system, the method being applied to an open circulating water system comprising a precooling device, a cooler and a control component, characterized in that: The pre-cooling device and the cooler are connected through a process material circulation pipeline. The pre-cooling device is arranged in front of the cooler according to the flow direction of the process material. The pre-cooling device cools the process material entering the pre-cooling device so that the temperature of the cooled process material is adapted to the circulating water temperature of the cooler, and the cooled process material is transported to the cooler through the process material circulation pipeline for further cooling. The specific steps of the method are: S1. First, the process material of the production device is cooled by pre-cooling equipment, and then the cooled process material is input into the cooler for cooling, so that the temperature of the cooled process material is compatible with the circulating water temperature of the cooler; S2. Model and analyze the circulating water supply pipeline system without cooling equipment, calculate the pressure loss of the pipe network system, set pressure measuring instruments at the inlet and outlet of each of the above coolers, and perform real-time pressure measurement. Among all the above pressure measurement data, find the three coolers with the lowest pressure, and mark the cooler with the lowest outlet pressure as the key line, the cooler with the second lowest outlet pressure as the sub-key line, and the other cooler as the attention line. Add pressure transmitters at the outlets of the three coolers marked as the key line, sub-key line, and attention line, respectively, to monitor the outlet pressure values ​​of the three coolers in real time; S3. Optimization of the cooling process of coolers with start-up coolers or one-on-one standby equipment: For equipment with start-up coolers, they are designed in a switchable manner in series and parallel with the coolers for low-level non-critical logistics, that is, when the device is started, it is put into use in parallel. After the production device operates normally, it is switched to the series mode, and the circulating water first enters the start-up cooler and then flows through the cooler for non-critical logistics; for the coolers of the one-on-one standby equipment, the two water-using equipment are set in a switchable manner in series and parallel. When the standby cooler needs to be started, it is switched to the parallel mode, and both coolers use water. When the equipment operates normally and the start-up cooler stops running, it is switched to the series mode, and the circulating water flows through the two coolers in sequence; S4. Method for adjusting the reasonable water consumption and real-time water consumption of the cooler: According to the reasonable water consumption of each cooler, the reasonable water consumption of each production device is obtained, and then the reasonable water consumption of the entire circulating water system is obtained; S41. Reasonable water consumption and reasonable flow rate of a single cooling device: The temperature of the reasonable water consumption of a single cooling device should meet the post-cooling temperature of the process material and the requirements of the process card or production operation. It can be calculated using heat transfer calculation software or judged based on the actual operation conditions on site; the temperature of the cooling water out of the cooler is less than or equal to 55°C; Reasonable flow rate of circulating water: When circulating water flows through the tube side, the flow rate of circulating water is 0.5m / s or above; when circulating water flows through the shell side, the flow rate of circulating water is 0.3m / s or above, and it is greater than 0.20m / s when anti-corrosion coatings or backwashing measures are taken; for the circulating water pipe side equipment that has been put into use, if the flow rate of circulating water cannot meet 0.5m / s or above, it can be achieved by blocking some heat exchange tubes; when pre-cooling equipment or pre-air cooler is set, the outlet temperature of process materials of the pre-cooling equipment or air cooler should be adjusted, and the flow rate of circulating water in the cooler should reach the above reasonable flow rate; S42. Adjustment of reasonable water volume and reasonable flow rate for cooling equipment with particularly large design margins: For water cooling equipment with particularly large design margins, some coolers shall not be put into use. While meeting the cooling requirements of process materials, the flow rate of circulating water in the cooling equipment shall reach a reasonable flow rate greater than 0.5m / s (circulating water pipe flow). When circulating water is flowing through the pipe flow, the reasonable flow rate shall be achieved by partially blocking the pipe and reducing the flow area of ​​the pipe flow. S43. Calculation method of real-time water consumption of a single cooling device: Based on process logistics and physical properties, the real-time data of the operating pressure, inlet temperature and outlet temperature of the process logistics are measured on the production device. A remote (local) thermometer is installed on the circulating water outlet pipeline of each cooler. Then: W = CP (logistics) × ΔT1 (logistics) / ΔT2 (circulating water) Where: W: is the consumption of circulating water CP (logistics): is the average specific heat capacity of process logistics ΔT1 (logistics): cooling temperature difference of process logistics, inlet temperature minus outlet temperature ΔT2 (circulating water): The temperature difference between the upper and lower water of the circulating water, the outlet temperature minus the inlet temperature CP (logistics) × ΔT1 (logistics): total cooling heat load of process materials in the cooler S44, real-time monitoring and operation method of water consumption: According to the comparison and judgment between the reasonable water consumption of each cooler and the real-time water consumption of soft measurement, if the deviation between the real-time water consumption and the reasonable water consumption is within ±10%, it is in good operation; if the deviation between the real-time water consumption and the reasonable water consumption is +10~20%, it means that the circulating water consumption is too much, and -10~20% means that the circulating water consumption is too little; if the deviation between the real-time water consumption and the reasonable water consumption is >20%, it means that the circulating water consumption is seriously too much, and <-20% means that the circulating water consumption is seriously too little; the operator shall make corresponding adjustments to the water consumption of the cooler according to the above judgment method of whether the water consumption is reasonable; S45, full parallel system water supply pressure and water supply pressure real-time adjustment method: When designing and selecting the circulating pump, the pressure that meets the water supply needs of the key lines in summer and under the condition of maximum processing volume should be selected, and an appropriate margin should be left; during the normal production process of the circulating water system, the theoretical calculated pressure loss of the pipeline should be compared with the measured pressure loss in real time; according to the real-time measurement values ​​of the pressure transmitters on the key lines, sub-key lines, and concerned lines, they should be associated with the circulating water pump to adjust the opening of the circulating water pump outlet valve; S46. For a system with a cooler that is arranged at a particularly high position or has a particularly large pressure loss, a booster pump needs to be added; a booster pump is added to the circulating water main pipe to increase the inlet pressure of the circulating water of the cooler, and the head of the booster pump is selected to ensure that the outlet pressure of the cooler is greater than zero; before the return water pipe of the cooler returns to the main pipe, a valve needs to be installed to reduce the pressure, and the pressure reduced by the valve is equivalent to the head of the booster pump to avoid increasing the total main pipe pressure after the return water of the cooler; S47. Operation optimization of circulating water pumps: The pumps of the circulating water system are all parallel systems. According to the operating characteristics of parallel pumps, the flow rate of a single circulating water pump is selected based on the principle that the actual number of pumps running in parallel should not exceed 4. The number of running pumps is N, and N-1 pumps should operate in the optimal efficiency zone of the pump. The Nth pump is used as a backup pump. When the actual efficiency of a pump is found to be low, the backup pump is started to check the use of the impeller of the pump with low actual efficiency.

2. The method for extending the operating period of an open circulating water system according to claim 1, characterized in that: In step S1, "reducing the cooling load of the cooler" specifically includes: setting a pre-cooling device at the process material entry side of the cooler to recover the heat of the process material before entering the cooler, thereby reducing the total cooling load of the cooler.

3. The method for extending the operating period of an open circulating water system according to claim 2, characterized in that: A temperature transmitter is provided on the process material discharge side of the pre-cooling equipment, and the outlet temperature of the process material is determined according to the properties of the process material and the cooling medium used by the pre-cooling equipment. The properties of the process material are non-toxic, non-harmful, non-severely corrosive, and non-abrasive fluid substances. When the cooling medium is pure liquid phase cooling, the temperature of the process material flowing out of the pre-cooling equipment is 75°C-100°C; or when the cooling medium is pure component condensation, the temperature of the process material flowing out of the pre-cooling equipment is lower than the condensation temperature of the cooling medium, and the temperature of the process material flowing out of the pre-cooling equipment is 75°C-100°C; or when the cooling medium is multi-component condensation, the temperature of the process material flowing out of the pre-cooling equipment is lower than 70-80% of the condensation temperature of the process material, and the temperature of the process material flowing out of the pre-cooling equipment is 75°C-100°C.

4. The method for extending the operating period of an open circulating water system according to claim 1, characterized in that: The fractionation tower uses direct heat pump, indirect heat pump, or tower heat coupling to reduce the temperature of process materials entering the cooler and reduce the total cooling load; For the overhead product of a fractionation tower such as a liquefied petroleum gas separation tower, where the temperature difference between the top and bottom is less than 20°C and there is basically no non-condensable gas, a compressor can be used to pressurize the overhead product to increase the temperature of the overhead product, and then the bottom product can be used as a heat source for the reboiler of the tower or other coupled towers; If the distillate from the top of the tower contains non-condensable gas or corrosive media, an indirect heat pump can be used to recover heat and reduce the cooling load; When multiple distillation towers are operated in series, when the steam tower temperature of the front tower is 20°C or more higher than the bottom temperature of the rear tower, the top steam of the front tower can provide all or most of the energy for the rear tower. The two towers are thermally coupled to reduce the heat source consumption of the low reboiler of the rear tower and the condensation load of the top gas phase of the front tower.

5. The method for extending the operating period of an open circulating water system according to claim 1, characterized in that: In step S1, "reducing the cooling load of the cooler" specifically includes: setting an air cooler on the water inlet side of the cooler to reduce the temperature of the process material entering the cooler and reduce the total cooling load of the cooler; Among them, a temperature transmitter is set on the outlet side of the air cooler, and the outlet temperature of the process material is determined according to the nature of the process material and the cooling medium used by the pre-cooling equipment. The nature of the process material is a non-toxic, non-harmful, non-severely corrosive, and non-abrasive fluid substance. When the cooling medium is pure liquid phase cooling, the temperature of the process material flowing out of the air cooler is 65℃-70℃; or when the cooling medium is pure component condensation, the temperature of the process material flowing out of the air cooler is 65℃-70℃; or when the cooling medium is multi-component condensation, the temperature of the process material flowing out of the air cooler is 65℃-70℃; Or in step S1, "reducing the cooling load of the cooler" is specifically as follows: a pre-cooling device and an air cooler are sequentially arranged on the process material entry side of the cooler, the heat of the process material is first recovered by the pre-cooling device, and then the process material with part of the heat recovered is cooled again by the air cooler, and finally the process material is cooled by the cooler to reduce the total cooling load of the cooler.

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