The present invention relates to a field of a chemical industry equipment and a chemical industry method, and in particular to a heat exchange device for atmospheric tower oil-gas and a heat exchange method thereof.

In the first working procedure for crude oil processing, according to different boiling points of components, an atmospheric and vacuum distillation unit divides the crude oil into naphtha, aviation kerosene, diesel, kerosene, vacuum residues and other fractions by distillation. The technical distillation level and the stable and efficient operation of this unit are directly relevant to the yield and economical benefits of the subsequent units. At present, the overall quality of the crude oil around the world declines, including declined global yield of light crude oil, rising sulfur content, aggregated oleic performance, and increased exploration difficulty, there is thus a large amount of Cl-containing auxiliaries in the processed crude oil. Accordingly, when the high-sulfur crude oil is processed by the atmospheric and vacuum distillation unit, due to a large amount of gas present on the oil-gas side on the atmospheric tower top, a high gas speed, corrosion resulted from ammonium salt crystalline deposit, HCl-H₂S-H₂O corrosion, scouring, occlusion resulted from ferrous sulfide or the like, an atmospheric tower top heat exchanger leaks or is occluded frequently, so that the long-period operation of the atmospheric and vacuum distillation unit is influenced greatly and it is likely to result in pollution of raw materials in downstream units. Accordingly, the normal operation of the downstream secondary processing units is influenced, and a great economic loss is caused. The units are generally constructed in such a manner that the corrosion is relieved by upgrading materials and enhancing corrosion-resistant measurements "one removal and three injections". Nevertheless, the corrosion and leakage of the atmospheric tower top heat exchanger are still very serious. Most atmospheric tower top heat exchangers are common heat exchangers. Although the grade of materials has been improved because of the anti-corrosion requirements, majority of such atmospheric tower top heat exchangers are still unable to operate for a long period, and tube bundles are likely to be corroded to result in leakage. Some of the atmospheric tower top heat exchangers are welded-plate heat exchangers. Although the materials of such heat exchanges are upgraded, it is likely to result in channel occlusion and leakage due to their poor fluctuation resistance and small circulation channel.

A first technical problem to be solved by the present invention is, in view of the prior art, to provide an heat exchange device for atmospheric tower oil-gas which can effectively avoid the occlusion of the heat exchanger so as to achieve the purpose of preventing the equipment from corrosion, prolonging the operating period and reducing the operating cost.

A second technical problem to be solved by the present invention is to provide an atmospheric tower oil-gas heat exchange method which can effectively avoid the occlusion of the heat exchanger.

To solve the first technical problem, the heat exchange device for atmospheric tower oil-gas comprises, a heat exchanger, the heat exchanger comprising a shell having a top, a bottom, a tube pass entrance and a tube pass exit; an upper tube plate and a lower tube plate which both are located within the shell; and supported between the upper tube plate and a lower tube plate; an inlet of each heat exchange tube connecting to a tube pass entrance arranged on the bottom of the shell, while an outlet of each heat exchange tube connecting to a tube pass exit arranged on the top of the shell, the tube pass exit and the tube pass entrance used for connecting crude oil flow; a shell pass entrance for connecting to an atmospheric tower oil-gas pipeline arranged on an upper portion of the shell; and a shell pass exit arranged on a lower portion of the shell; characterized in that:

an annular water injection pipe connected to an external water injection pipeline is arranged within the upper portion of the shell, the annular water injection pipe has multiple water pores communicated to the interior of the shell; the atmospheric tower oil-gas pipeline is connected to the external water injection pipeline via a first water injection pipeline and a third water injection pipeline; a first solenoid valve and a second solenoid valve are respectively arranged on the first water injection pipeline and the third water injection pipeline; and, the annular water injection pipe is communicated to the external water injection pipeline via a second water injection pipeline.

Preferably, the shell has a water inlet, and the external water injection pipeline is communicated to the annular water injection pipe via the water inlet.

Preferably, the annular water injection pipe is located below the upper tube plate and close to the upper tube plate.

Preferably, each heat exchange tube between the upper tube plate and the lower tube plate is coiled around a central axis of the shell.

Preferably, a gas outlet, which is communicated to the interior of the shell and used for exhausting gas on the top of the shell during maintenance, is further arranged on the top of the shell, and a liquid outlet for discharging liquid on the bottom of the shell during maintenance is further arranged on the bottom of the shell.

Preferably, each of the heat exchange tubes is a pure-titanium heat exchange tube.

To solve the second technical problem, the heat exchange method using the heat exchange device for atmospheric tower oil-gas provided in the above solutions, comprises the following steps:

• feeding crude oil into the heat exchange tubes of the heat exchanger, mixing atmospheric tower oil-gas with a first stream of injected water and then passing it to the shell of the heat exchanger, exchanging heat with the crude oil, and then discharging it from the heat exchanger to the downstream, wherein a flow ratio of the crude oil to the atmospheric tower oil-gas is (4-5) :1, the amount of the first stream of injected water is 2% to 3% of the flow of the atmospheric tower oil-gas, the atmospheric tower oil-gas has a temperature of 120°C to 150°C and a pressure of 0.10 MPaG to 0.15 MPaG, the first stream of injected water has a temperature of 30°C to 50°C and a pressure of 2.0 MPaG to 2.5 MPaG, and the temperature at the shell pass exit after the heat exchanging is 80°C to 85°C;
• feeding a second stream of injected water continuously into the annular water injection pipe, and then spraying the second stream of injected water into the shell from the water pores, wherein a ratio of the flow of the second stream of injected water to the flow of the first stream of injected water is (3-4) :1, and the temperature of the second stream of injected water is 30°C to 50°C; and
• feeding a third stream of injected water intermittently into the atmospheric tower oil-gas pipeline and then into the shell pass from the shell pass entrance, wherein a ratio of the flow of the third stream of injected water to the flow of the first stream of injected water is (8-12) :1, the temperature of the third stream of injected water is 30°C to 50°C, the water injection lasts for 25 min to 35 min, and the water injection period is 80 min to 100 min.

Compared with the prior art, in the heat exchange device for atmospheric tower oil-gas and heat exchange method of the present invention, under feeding water to the oil-gas pipeline and washing the shell by the annular water injection pipe, the heat exchange efficiency is effectively improved, the anti-fouling performance is excellent and the resistance against HCl-H₂S-H₂O corrosion and under-deposit corrosion is great. Moreover, the stubborn phenomena such as corrosion resulted from ammonium salt crystalline deposit and occlusion resulted from ferrous sulfide are avoided, and the problems of frequent occlusion and leakage or even replacement of the atmospheric tower oil-gas/crude oil head exchanger due to its easy corrosion, leakage, channel occlusion or other factors are solved. Meanwhile, the device has a small pressure drop and a stable operation, so that the safe operating period of the device is greatly increased.

• FIG. 1 is a perspective view of the heat exchanger according to an embodiment of the present invention;
• FIG. 2 is a flowchart of a process according to an embodiment of the present invention;
• Fig. 3 is a plan view of Fig. 1 in a direction A;
• Fig. 4 is a plan view of Fig. 1 in a direction B; and
• Fig. 5 is a sectional view of Fig. 1 in a longitudinal direction.

To enable a further understanding of the present invention content of the invention herein, refer to the detailed description of the invention and the accompanying drawings below:

Fig. 1 - Fig.5 show a preferred embodiment of the present invention. The heat exchange device for atmospheric tower oil-gas comprises:

• a heat exchanger 1 comprising a shell 11, wherein a tube pass exit 18 communicated to each heat exchange tube 5, a water inlet 15 communicated to a second water injection pipeline 32, a gas outlet 10 communicated to the interior of the shell, and a shell pass entrance 12 on a side wall of an upper seal of the heat exchanger are provided on the top of the shell 11 at intervals; and a tube pass entrance 13 communicated to each heat exchange tube 5, a shell pass exit 14 communicated to the interior of the shell and a liquid outlet 19 are provided on the bottom of the shell 11 at intervals.

An upper tube plate 16 and a lower tube plate 17 are further provided inside the shell 11.

There is a plurality of heat exchange tubes 5, each heat exchange tube 5 is a pure-titanium heat exchange tube for ensuring the anti-corrosion performance of the heat exchange tubes. Upper and lower ends of each of the heat exchange tubes are fixed on the upper tube plate and the lower tube plate respectively. A portion of each heat exchange tubes between the upper tube plate 16 and the lower tube plate 17 is coiled around a central axis of the shell 11 in order to improve the heat exchange efficiency.

An annular water injection pipe 6 is provided inside the shell 11 and located close to the upper tube plate 16 and below the upper tube plate 16. Multiple water pores 61 communicated to the interior of the shell are uniformly distributed on the wall of the annular water injection pipe 6. An inlet of the annular water injection pipe 6 is connected to a second water injection pipeline 32 via the water inlet 15.

A shell pass entrance 12 is connected to an atmospheric tower oil-gas pipeline 2, a first water injection pipeline 31 and a third water injection pipeline 33 are connected onto the atmospheric tower oil-gas pipeline 2, and both the first water injection pipeline 31 and the third water injection pipeline 33 are connected to an external water injection pipeline 3; and a first solenoid valve 34 and a second solenoid valve 35 are respectively arranged on the first water injection pipeline 31 and the third water injection pipeline 33.

Water is fed into the atmospheric tower oil-gas pipeline 2 via the first water injection pipeline 31. The solenoid valves are used for adjusting the water flow. The third water injection pipeline is used for intermittently injecting water into the atmospheric tower oil-gas pipeline 2 for purpose of washing the shell pass at a large water flow.

Both the first water injection pipeline 31 and the third water injection pipeline 33 are connected to the external water injection pipeline 3, and solenoid valves are respectively provided on the first water injection pipeline 31 and the third water injection pipeline 33. The two solenoid valves are connected to a control system (not shown in the Figs). The ON, OFF and degree of opening of the two solenoid valves are controlled by the control system, so that the water injection by each water injection pipeline is controlled.

A heat exchange method using the atmospheric tower oil-gas head exchange device described above is provided, comprising the following steps:

feeding crude oil through a crude oil pipeline 7 into the heat exchange tubes from the tube pass entrance, mixing atmospheric tower oil-gas from an atmospheric tower 8 with a first stream of injected water and then passing it to the shell of the heat exchanger from the shell pass entrance, exchanging heat with the crude oil, and then discharging it from the shell pass exit to the downstream, wherein the atmospheric tower oil-gas has a flow of 43860 kg/h, a temperature of 125°C, a pressure of 0.11 MPaG, and a temperature of 82°C at the outlet after the heat exchange; the first stream of injected water has a flow of 1000 kg/h and a temperature of 40°C; and the crude oil has a flow of 192400 kg/h, a temperature of 32°C at the inlet, a pressure of 2.1 MPaG, and a temperature of 72°C at the outlet after the heat exchange;

feeding a second stream of injected water continuously into the water injection pipe 6, and then spraying the second stream of injected water into the shell from the water pores 61, wherein the amount of the second stream of injected water is controlled at 3000 kg/h to 4000 kg/h, and the temperature is 40°C; and

feeding a third stream of injected water intermittently into the atmospheric tower oil-gas pipeline 2, wherein the amount of the third stream of injected water is controlled at 10000 kg/h, the temperature is 40°C, the water injection lasts for 30 min, and the water injection period is 90 min. The flow and duration of the first stream of injected water and the third stream of injected water are controlled by the two respective solenoid valves.

During maintenance, the medium in the equipment needs to be discharged completely. The gas outlet 10 is opened to exhaust atmospheric tower oil-gas gathered in the upper portion of the shell. The equipment is disassembled and then washed. Cleaning liquid is injected from the gas outlet 10 and drained from the liquid outlet 19.

The service life of an existing common atmospheric tower top heat exhauster is about 1 to 2 years, and the whole existing common atmospheric tower top heat exhauster or the whole tube bundle needs to be replaced when corrosion and leakage occur. The existing common atmospheric tower top heat exchanger needs to be frequently cleaned due to channel occlusion. In the heat exchange device and heat exchange method provided by the present invention, the equipment body has excellent corrosion resistance and anti-fouling performance, and within two operating periods (i.e., 8 years), no fouling (thus occlusion) and corrosion (thus leakage) occurs. Therefore, a large amount of cost for equipment replacement and maintenance is saved.