Hot nitrogen defrosting system

Abstract

The utility model relates to a hot nitrogen defrosting system. The hot nitrogen defrosting system comprises a heat exchanger, a chemical oil gas main pipeline; the number of the heat exchange cold boxes is two, and each heat exchange cold box is provided with a chemical oil gas inlet pipe and a chemical oil gas outlet pipe; a nitrogen defrosting line; a valve II is arranged on the nitrogen defrosting loop pipeline; due to the fact that the nitrogen defrosting pipeline and the nitrogen defrosting loop pipeline are both connected with the two heat exchange cold boxes in parallel, namely, a hot nitrogen defrosting system formed by the nitrogen defrosting pipeline and the nitrogen defrosting loop pipeline runs completely independently, compressor faults caused by refrigerant return air with liquid can be completely avoided, normal running of production equipment is powerfully guaranteed, and the nitrogen defrosting system is simple in structure, easy to operate and low in cost. Compared with the prior art, an original defrosting mode is optimized, the situation that the refrigerating effect is affected due to material mixing of a defrosting agent and a refrigerant is avoided, meanwhile, air entraining and pre-cooling defrosting operation of the same system can be carried out, and the problem of a tail gas treatment vacuum period caused by channel blockage is effectively solved.

Description

Technical Field

[0001] The utility model relates to the technical field of condensation system defrosting, in particular to a hot nitrogen defrosting system. Background Art

[0002] The oil and gas recovery system uses the internal temperature of the heat exchange cold box (evaporator) to be lower than the dew point temperature of the mixed oil and gas to liquefy and recover the oil and gas during the condensation recovery process. Since the oil and gas processed by our company generally have a low condensation point and there is water vapor in the mixed tail gas, frosting is also the result of the normal operation of the condensation recovery system. Since the thermal conductivity of the frost layer is poor and the thick frost layer affects the normal introduction of oil and gas, the original system uses the hot gas defrosting mode for defrosting operation. Through our company's field use, it is found that the defrosting system technology is still insufficient. The existing problems are as follows:

[0003] (1) The original defrosting automatic control program has defects and cannot achieve automatic defrosting. Currently, manual defrosting is required, which is inefficient, labor-intensive, and difficult to manage. It cannot be controlled in real time and poses a safety hazard.

[0004] (2) The original system used hot gas defrosting, which was complex in process, poor in effect, long in defrosting time, and high in energy consumption. In addition, since the high-temperature hot gas of the refrigerant was used for defrosting, it was very easy to cause a large amount of liquid backflow and liquid hammer in the unit, affecting the normal use of the facility.

[0005] (3) The original defrost system was complex and had no bypass line. The valve core was made of cast steel rather than high-strength steel. After long-term operation, the sealing device was easily damaged, causing internal leakage of the valve, resulting in cross-talk between the defrost agent and the refrigerant, affecting the refrigeration effect.

[0006] Based on this, we have improved the hot nitrogen defrost system of the current condensation system to meet the defrost process requirements. Utility Model Content

[0007] The technical problem to be solved by the utility model is to provide an exhaust condensate collection device which, in view of the defrosting defects of the prior art, has a safer defrosting medium, a higher defrosting efficiency, a shorter stroke and no energy loss, and a simple structure, and will not affect the operation of the refrigeration unit during the defrosting process.

[0008] The technical problem to be solved by the utility model is achieved through the following technical solution: a hot nitrogen defrosting system, the hot nitrogen defrosting system comprising:

[0009] A chemical oil and gas main pipeline, which is used to transport chemical oil and gas, and is provided with a chemical oil and gas pressurizing blower;

[0010] Heat exchange cold boxes, two of which are provided, each of which has a chemical oil and gas inlet pipe and a chemical oil and gas outlet pipe, and the outlet end of the chemical oil and gas main pipeline is connected in parallel with the chemical oil and gas inlet pipes of the two heat exchange cold boxes through a three-way valve;

[0011] A nitrogen defrost pipeline, the outlet of which is connected in parallel to the chemical oil and gas inlet pipes of the two heat exchange cold boxes through a three-way valve, and a valve I and an electric heater are provided on the nitrogen defrost pipeline;

[0012] The nitrogen defrost loop pipeline has its inlet end connected in parallel with the chemical oil and gas outlet pipes of the two heat exchange cold boxes through a three-way valve, and its outlet end is connected to the chemical oil and gas main pipeline. A valve II is provided on the nitrogen defrost loop pipeline.

[0013] The technical problem to be solved by the utility model can also be achieved through the following technical solutions. The above-mentioned condensation recovery temperature automatic control adjustment system is provided with a temperature transmitter in the heat exchange cold box. The temperature transmitter is located on the heat exchange grid in the heat exchange cold box. The temperature transmitter is interlocked with valve I.

[0014] The technical problem to be solved by the utility model can also be achieved through the following technical scheme. The above-mentioned condensation recovery temperature automatic control adjustment system also includes a fan auxiliary line, and the two ends of the fan auxiliary line are connected in parallel to the chemical oil and gas main pipeline, and an auxiliary chemical oil and gas pressurization fan is arranged on the fan auxiliary line.

[0015] The technical problem to be solved by the utility model can also be achieved through the following technical solutions. In the above-mentioned condensation recovery temperature automatic control adjustment system, a flow meter is arranged on the chemical oil and gas main pipeline.

[0016] Compared with the prior art, the beneficial technical effects of the utility model are:

[0017] (1) Since the nitrogen defrost pipeline and the nitrogen defrost loop pipeline are connected in parallel with the two heat exchange cold boxes, the hot nitrogen defrost system they constitute is completely independent, which can completely avoid the occurrence of compressor failure caused by liquid in the refrigerant return gas, effectively ensuring the normal operation of the production equipment. In addition, the structure is simple and easy to operate. The original defrosting method is optimized to ensure that the defrost agent and refrigerant will not mix and affect the refrigeration effect. At the same time, the same system can be used for air induction and pre-cooling defrosting operations, effectively solving the vacuum period problem caused by channel blockage;

[0018] (2) The original defrost system used a complex exhaust process for the refrigeration unit, consumed a lot of energy, and the control method was not smooth, which affected safe and stable operation. The hot nitrogen defrost system optimized the problems caused by the defrosting part of the condensing system, added valves I, II and some three-way valves, played a role in precise control, reduced human interference, and made the defrost system fast, efficient, safe and accurate.

[0019] (3) Due to the particularity of the company's wharf area, low-pressure steam is introduced from the onshore tank area. The main line is long (15 km) and has high maintenance costs. The steam flow rate consumed per hour is 10 t / h, while the traditional hot gas defrosting system steam heating design consumption is only 0.01 t / h. If low-pressure steam is used under necessary conditions outside winter (8 months), the steam loss is 55,000 tons. This part of the steam loss includes the inevitable energy loss during the transportation of steam in the park pipeline. The use of the hot nitrogen defrosting method of the present application for defrosting saves a large amount of steam, which means that hot nitrogen defrosting is more economical in terms of energy consumption cost.

[0020] (4) The original defrost system uses hot gas defrosting agent and refrigerant together in the heat exchange cold box. Since the pneumatic valve is made of cast steel, there is a possibility of corrosion. At the same time, the sealing is reduced after long-term opening and closing. The high-temperature defrosting agent and the refrigerant are connected, which seriously affects the refrigeration effect. The hot nitrogen defrosting system has a simple structure and uses hot nitrogen to directly act on the frost layer. It has a short stroke, high heat utilization rate, and can quickly defrost. At the same time, the melted frost layer oil and gas return to the beginning of the condensation recovery unit, that is, the chemical oil and gas main pipeline, for further treatment, avoiding pollution to the atmospheric environment and having strong operability. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a structural schematic diagram of the utility model.

[0022] In the figure, 1. Chemical oil and gas main pipeline; 2. Chemical oil and gas pressurizing fan; 3. Fan auxiliary line; 4. Auxiliary chemical oil and gas pressurizing fan; 5. Valve II; 6. Heat exchange cold box; 7. Chemical oil and gas inlet pipe; 8. Chemical oil and gas outlet pipe; 9. Nitrogen defrost pipeline; 10. Valve I; 11. Electric heater; 12. Nitrogen defrost loop pipeline. DETAILED DESCRIPTION

[0023] The specific technical solutions of the present invention are further described below with reference to the accompanying drawings, so as to facilitate further understanding of the present invention by those skilled in the art, and do not constitute any limitation to the rights thereof.

[0024] Example 1, reference Figure 1 , a hot nitrogen defrost system, the hot nitrogen defrost system comprising;

[0025] The chemical oil and gas main pipeline 1 is used to transport chemical oil and gas, which comes from the organic matter discharged during the loading and unloading process of terminal oil and chemical products. A chemical oil and gas pressurizing fan 2 is arranged on it, and the chemical oil and gas pressurizing fan 2 sends this part of the chemical oil and gas to the heat exchange cold box 6 described below;

[0026] In order to improve the overall stability of the system, we have added a fan auxiliary line 3 on the original basis. The two ends of the fan auxiliary line 3 are connected in parallel to the chemical oil and gas main pipeline 1. A secondary chemical oil and gas pressurizing fan 4 is set on the fan auxiliary line 3. When the initial chemical oil and gas pressurizing fan 2 is damaged, the secondary chemical oil and gas pressurizing fan 4 can be activated to facilitate the maintenance and repair of the initial chemical oil and gas pressurizing fan 2.

[0027] In order to monitor the chemical oil and gas delivery volume of the chemical oil and gas main pipeline 1, a flow meter is installed on the chemical oil and gas main pipeline 1 for easy observation;

[0028] Heat exchange cold box 6, two heat exchange cold boxes 6 are provided, each heat exchange cold box 6 has a chemical oil and gas inlet pipe 7 and a chemical oil and gas outlet pipe 8, and the outlet end of the chemical oil and gas main pipeline 1 is connected in parallel with the chemical oil and gas inlet pipes 7 of the two heat exchange cold boxes 6 through a three-way valve;

[0029] That is to say, the chemical oil and gas main pipeline 1 can selectively transport chemical oil and gas to one of the heat exchange cold boxes 6, so that the two heat exchange cold boxes 6 are completely independent equipment, which is convenient for subsequent switching operations;

[0030] In order to facilitate the defrosting of the heat exchange cold box 6, a nitrogen defrosting pipeline 9 is specially set up, and its outlet end is connected in parallel with the chemical oil and gas inlet pipes 7 of the two heat exchange cold boxes 6 through a three-way valve, so that any heat exchange cold box 6 can be defrosted. A valve I 10 and an electric heater 11 are provided on the nitrogen defrosting pipeline 9. The electric heater 11 is an existing technology and can be selected according to the use requirements;

[0031] A temperature transmitter (not shown) is provided in the heat exchange cold box 6. The temperature transmitter is a prior art and its model and specification can be selected according to the use requirements. The temperature transmitter is located in the heat exchange cold box 6 and is located on the heat exchange grid (not shown) provided in the heat exchange cold box 6.

[0032] In order to facilitate the control of the nitrogen delivery volume, we interlock the temperature transmitter with valve Ⅰ10. When the temperature transmitter detects a low temperature, the nitrogen delivery volume can be appropriately increased. When the detected temperature is high, the nitrogen delivery volume can be appropriately reduced. This allows for flexible control. The specific numerical ratio can be customized according to usage requirements.

[0033] In order to avoid unnecessary pollution of the atmosphere by the defrosted gas, we have added a nitrogen defrost loop pipeline 12, the inlet end of which is connected in parallel with the chemical oil and gas outlet pipes 8 of the two heat exchange cold boxes 6 through a three-way valve, and the outlet end is connected to the chemical oil and gas main pipeline 1, so that the defrosted oil and gas are returned to the beginning of the condensation recovery unit, i.e., the chemical oil and gas main pipeline 1. A valve II5 is provided on the nitrogen defrost loop pipeline 12.

[0034] The operating principle of the hot nitrogen defrost system is:

[0035] Take one of the heat exchange cold boxes 6 in use as equipment A, and the other heat exchange cold box 6 as equipment B. When equipment A needs to be shut down for operation and maintenance, the nitrogen defrosting pipeline 9 first supplies nitrogen to equipment B, during which the electric heater 11 is turned on and heated to 100°C. At this time, the hot nitrogen enters equipment B for defrosting. After a certain period of defrosting, the nitrogen supply is stopped, and the three-way valve between the chemical oil and gas main pipeline 1 and equipment A and B can be switched, so that the gas supply state to equipment A is switched to gas supply to B. At this time, the shutdown equipment A can be operated and maintained;

[0036] Similarly, when it is necessary to switch the running device B to the device A, it is only necessary to defrost the device A through the nitrogen defrosting circuit pipeline 12. After the defrosting operation is completed, the state of gas supply to the device B can be switched to gas supply to the device A in the same manner as above;

[0037] On the one hand, compared with the traditional hot gas defrosting system, the steam heating design consumption is only 0.01t / h. If low-pressure steam is used under necessary conditions outside winter (8 months), the steam loss is 55,000t, which includes the inevitable energy loss during the transportation of steam in the park pipeline. The hot nitrogen defrosting system is more economical and environmentally friendly, and has played a role in reducing costs, increasing efficiency and improving production capacity to a certain extent.

[0038] On the other hand, the defrosted gas flow directly reaches the front end of the chemical oil and gas main pipeline 1 through the nitrogen defrost loop pipeline 12, and undergoes subsequent treatment again to avoid direct discharge of this part of the gas into the atmosphere and causing unnecessary pollution.

Claims

1. A hot nitrogen defrost system, characterized in that: The hot nitrogen defrost system comprises: A chemical oil and gas main pipeline, which is used to transport chemical oil and gas, and is provided with a chemical oil and gas pressurizing blower; Heat exchange cold boxes, two of which are provided, each of which has a chemical oil and gas inlet pipe and a chemical oil and gas outlet pipe, and the outlet end of the chemical oil and gas main pipeline is connected in parallel with the chemical oil and gas inlet pipes of the two heat exchange cold boxes through a three-way valve; A nitrogen defrost pipeline, the outlet of which is connected in parallel to the chemical oil and gas inlet pipes of the two heat exchange cold boxes through a three-way valve, and a valve I and an electric heater are provided on the nitrogen defrost pipeline; The nitrogen defrost loop pipeline has its inlet end connected in parallel with the chemical oil and gas outlet pipes of the two heat exchange cold boxes through a three-way valve, and its outlet end is connected to the chemical oil and gas main pipeline. A valve II is provided on the nitrogen defrost loop pipeline.

2. A hot nitrogen defrost system according to claim 1, characterized in that: A temperature transmitter is arranged in the heat exchange cold box. The temperature transmitter is located on the heat exchange grid provided in the heat exchange cold box. The temperature transmitter is interlocked with valve I.

3. A hot nitrogen defrost system according to claim 1, characterized in that: It also includes a fan auxiliary line, both ends of which are connected in parallel to the chemical oil and gas main pipeline, and an auxiliary chemical oil and gas pressurizing fan is arranged on the fan auxiliary line.

4. A hot nitrogen defrost system according to claim 1, characterized in that: The chemical oil and gas main pipeline is provided with a flow meter.

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