Method for cleaning internal surfaces of pipelines with supercritical carbon dioxide

Abstract

FIELD: pipeline cleaning.SUBSTANCE: invention relates to methods of cleaning using liquid and can be used in various fields of industry for cleaning pipelines from oil and operational contaminants. A method for cleaning the internal surfaces of pipelines with supercritical carbon dioxide, in which carbon dioxide is used as the working medium, which is in a supply tank in a liquid state, which is supplied to a pump, the pressure of the working medium is maintained above the critical pressure for carbon dioxide, the working medium is heated to a temperature above the critical temperature for carbon dioxide, thereby converting carbon dioxide into a supercritical fluid state, the working medium is directed to the pipeline to be flushed, where it is flushed using the working medium, after which the working medium is cooled to a temperature below the critical temperature for carbon dioxide, thus converting carbon dioxide into a liquid state, then the working medium passes through a filter and returns to the supply tank, whereas at first the circulation circuit of the working medium is filled with liquid carbon dioxide from a make-up cylinder, the pump circulating the working medium is located in the supply tank, the pressure of the working medium required for the transition of the working medium to a supercritical fluid state is created by feeding nitrogen from a pressure cylinder into the gas cap of the supply tank, the working medium is heated to a temperature above the critical temperature for carbon dioxide and cooling the working environment to a temperature below the critical temperature for carbon dioxide using Peltier elements.EFFECT: simplification of the design of an installation for cleaning the internal surfaces of pipelines with supercritical carbon dioxide.1 cl, 1 dwg

Description

[0001] The claimed technical solution relates to cleaning methods using liquid and can be used in various industrial fields to clean pipelines from oil and operational contaminants.

[0002] A known method of hydrodynamic cleaning (B.V. Soloviev. Cleaning ship systems from technological contaminants. Leningrad, Shipbuilding: 1977, pp. 18-22), in which the working medium from the supply tank enters the pump, then is directed along the pressure line to the product being washed, the said product is washed with the working medium using technological methods for intensifying the washing process, for example, vibration and turning of the product being washed, pressure pulsation and flow rate of the working medium, and then the working medium returns through filters to the supply tank.

[0003] The disadvantage of this method is the unsatisfactory quality of cleaning pipelines heavily contaminated with oils and operational contaminants, the need to use additional technological methods to intensify the cleaning process to improve its quality.

[0004] A known method for cleaning hydraulic system pipelines from oil and operational contaminants with supercritical carbon dioxide (Patent No. 2699628, Russian Federation, IPC B08B 3 / 00, B08B 9 / 027, B08B 7 / 00 "Method for cleaning hydraulic system pipelines from oil and operational contaminants with supercritical carbon dioxide" / Sosnina Yu.N., Pospelova A.V., Kulikov K.N., applicant and patent holder Joint Stock Company Scientific Research Design and Technology Bureau Onega (JSC NIPTB Onega) - No. 2019110964), in which the working medium from the supply tank enters the pump, then is directed through the pressure line to the pipeline being washed, flushing of the specified flushed pipeline with the working medium, and then the working medium returns through the filter to the supply tank, after the pump the working medium enters the evaporator of the recuperative system for maintaining the temperature regime, which includes the evaporator,a condenser and a compressor of the refrigerant circulating in the said system, which heats it to a temperature above the critical temperature for carbon dioxide, thus converting carbon dioxide into a supercritical fluid state; after cleaning, the working medium passes through the condenser of the recuperative temperature maintenance system, cooling it to a temperature below the critical temperature for carbon dioxide; the filter through which the working medium passes before returning to the supply tank is a coalescent filter, and the residual carbon dioxide from the flushed pipeline is removed into the atmosphere after flushing.

[0005] The disadvantage of this method is the complexity of the design of the installation intended for its implementation.

[0006] The essence of the claimed technical solution is that in the known method for cleaning hydraulic system pipelines from oil and operational contaminants with supercritical carbon dioxide, carbon dioxide is used as a working medium, which is in a supply tank in a liquid state, which is supplied to the pump, the pressure of the working medium is maintained above the critical pressure for carbon dioxide, the working medium is heated to a temperature above the critical temperature for carbon dioxide, thereby converting carbon dioxide into a supercritical fluid state, the working medium is directed to the pipeline to be washed, where it is washed using the working medium, after which the working medium is cooled to a temperature below the critical temperature for carbon dioxide, thus, carbon dioxide passes into a liquid state, then the working medium passes through the filter and returns to the supply tank,In this case, the working medium circulation circuit is first filled with liquid carbon dioxide from a make-up cylinder, the pump that circulates the working medium is located in the supply tank, the working medium pressure required for the working medium to transition to a supercritical fluid state is created by feeding nitrogen from a pressure cylinder into the gas cap of the supply tank, the working medium is heated to a temperature above the critical temperature for carbon dioxide and cooled to a temperature below the critical temperature for carbon dioxide is carried out using Peltier elements.

[0007] Thus, the claimed technical solution differs from the prototype in that the working medium circulation circuit is first filled with liquid carbon dioxide from a make-up cylinder, the pump that circulates the working medium is located in the supply tank, the working medium pressure required for the working medium to transition to a supercritical fluid state is created by feeding nitrogen from a pressure cylinder into the gas cap of the supply tank, the working medium is heated to a temperature above the critical temperature for carbon dioxide and the working medium is cooled to a temperature below the critical temperature for carbon dioxide using Peltier elements.

[0008] A comparative analysis of this technical solution with others showed that the specified set of features will allow for a simplification of the design of a unit for cleaning the internal surfaces of pipelines with supercritical carbon dioxide.

[0009] Filling the working fluid circulation circuit with liquid carbon dioxide from a make-up cylinder, together with supplying nitrogen from a pressure cylinder to the gas cap of the supply tank to create the working fluid pressure necessary for the working fluid to transition to a supercritical fluid state, as well as placing the pump that circulates the working fluid in the supply tank, allows for reducing the requirements for the pump power and the accuracy of its adjustment, since in this case it is not required to create the working fluid pressure necessary for the working fluid to transition to a supercritical fluid state.

[0010] Thus, when creating a unit for cleaning the internal surfaces of pipelines with supercritical carbon dioxide, it is possible to choose a pump with a simpler design and lower power, also without precision adjustment mechanisms and high-precision pressure sensors.

[0011] The working fluid circulation circuit, as well as its required pressure, in the claimed technical solution are filled using carbon dioxide and nitrogen cylinders, which are widely used in various industrial facilities and do not require complex additional equipment. Furthermore, by supplying nitrogen from a pressure cylinder to the gas cap of the supply tank to create the working fluid pressure necessary for the working fluid to become a supercritical fluid, it is possible, by adjusting the nitrogen supply, to easily change the working fluid pressure to achieve the desired level without having to change the pump operating mode.

[0012] In general, this solution is simpler and easier to implement in industrial enterprises.

[0013] Heating the working fluid to a temperature above the critical temperature for carbon dioxide and cooling the working fluid to a temperature below the critical temperature for carbon dioxide are accomplished using Peltier elements. This eliminates the need for a complex recuperative temperature maintenance system, replacing it with simple and compact Peltier elements that have no moving parts and are easier to operate and maintain, while still allowing flexible temperature control of the working fluid. This also eliminates the complexities of handling the refrigerant circulating in the recuperative temperature maintenance system.

[0014] Fig. 1 shows a diagram of an installation for cleaning the internal surfaces of pipelines with supercritical carbon dioxide.

[0015] The installation for cleaning the internal surfaces of pipelines with supercritical carbon dioxide includes a pressure cylinder 1, a make-up cylinder 2, a supply tank 3, a pump 4, a flow meter 5, a heat exchanger with heat supply 6, a hose 7, a flushed pipeline 8, a heat exchanger with heat removal 9, a filter 10, a shut-off valve 11, a pressure gauge 12, a safety device 13, a thermometer 14. The heat exchanger with heat supply 6 and the heat exchanger with heat removal 9 are adjacent to opposite faces of a Peltier element (not indicated), designed to provide multidirectional heat exchange by removing heat from the heat exchanger with heat removal 9 to the heat exchanger with heat supply 6.

[0016] The claimed method is carried out as follows:

[0017] Using flexible hoses 7, the pipeline 8 being flushed is connected to a supercritical carbon dioxide cleaning system. The working fluid—liquid carbon dioxide—is supplied from the make-up cylinder 2 to fill the working fluid circulation circuit. To transform the carbon dioxide into a supercritical state, the pressure and temperature must be increased above the critical point (7.39 MPa and 31°C). For optimal operation of the system, the following technical specifications were adopted: a pressure of 12 MPa and a temperature of 35°C.

[0018] The pressure is increased to the required parameters by feeding nitrogen from the pressure cylinder 1 into the gas cap of the supply tank 3. The working medium is circulated by the pump 4 installed in the supply tank 3. The flow rate of the working medium is monitored by the flow meter 5. To transform the working medium into a supercritical state, it is necessary to heat the working medium in the heat exchanger 6 before the flushed pipeline 8. The working medium in a supercritical state passes through the flushed pipeline 8, cleaning it. After the sleeve 7, the working medium enters the heat exchanger 9, where it is cooled to plus 5 °C to transform the working medium into a liquid state. The working medium enters the filter 10, where the working medium is separated from the oil and operational contaminants. The cleaned working medium is returned to the supply tank 3. A pressure gauge 12 and a thermometer 14 are provided to monitor the parameters of the medium.To protect against pressure exceeding the permissible value in the circuit, a safety device 13 is provided. The process is repeated cyclically until the flushed pipeline 8 is completely cleared of oil contaminants.

[0019] The claimed technical solution will allow for a simplified design of a plant for cleaning the internal surfaces of pipelines with supercritical carbon dioxide.

Claims

A method for cleaning the internal surfaces of pipelines with supercritical carbon dioxide, in which carbon dioxide is used as the working medium, which is in a supply tank in a liquid state, which is supplied to a pump, the pressure of the working medium is maintained above the critical pressure for carbon dioxide, the working medium is heated to a temperature above the critical temperature for carbon dioxide, thereby converting carbon dioxide into a supercritical fluid state, the working medium is directed to the pipeline to be washed, where it is washed with the working medium, after which the working medium is cooled to a temperature below the critical temperature for carbon dioxide, thus converting carbon dioxide into a liquid state, then the working medium passes through a filter and returns to the supply tank, characterized in that the circulation circuit of the working medium is first filled with liquid carbon dioxide from a make-up cylinder, a pump,circulating the working medium, is located in the supply tank, the pressure of the working medium required for the transition of the working medium to the state of a supercritical fluid is created by feeding nitrogen from a pressure cylinder into the gas cap of the supply tank, heating the working medium to a temperature above the critical temperature for carbon dioxide and cooling the working medium to a temperature below the critical temperature for carbon dioxide is carried out using Peltier elements.

Images