Electric boiler with waste heat recovery function

Abstract

The utility model discloses an electric boiler with a waste heat recovery function, which comprises an electric boiler body, a waste heat recovery device and a waste heat recovery device, the heat exchange box is filled with water; the same connecting pipe is communicated and fixed between the left side of the top of the round box body and the top end of the flue gas discharge pipe; and the round rotating seat is movably sleeved in the round box body. By arranging a series of structures, smoke dust particle impurities in smoke can be filtered and intercepted, the entering effect of the smoke is enhanced by means of actively providing suction force through the air pump, the phenomenon that the smoke naturally flows and is difficult to smoothly penetrate through a stainless steel filter screen to enter or smoke suffocation occurs is reduced, the flowing stability is improved, and the service life of the smoke purifier is prolonged. And meanwhile, the multiple stainless steel filter screens can be subjected to circulating filtration and utilization, integral circulating back-blowing cleaning and dredging and deslagging are achieved, blockage caused by the fact that smoke dust particle impurities are statically stacked and cover the surfaces of the stainless steel filter screens is avoided, long-acting stable smooth filtration work is guaranteed, and smooth filtration stability is improved.

Description

Technical Field

[0001] This utility model relates to the field of boiler technology, specifically to an electric boiler with waste heat recovery function. Background Technology

[0002] A boiler is an energy conversion device. The energy input to a boiler includes the chemical energy of fuel and electrical energy. The boiler outputs steam, high-temperature water or organic heat carrier with a certain amount of thermal energy. When thermal power plants recover waste heat from boilers, the general method is to directly export the flue gas discharged from the boiler for heat exchange and utilization.

[0003] In response, CN219607780U discloses a boiler with waste heat recovery function, comprising: a boiler body, with a connecting pipe connected to the right side of the boiler body; a heat exchange box, located on the right side of the boiler body, with a heat-conducting pipe inside the heat exchange box extending to the outside of the heat exchange box; an exhaust pipe, connected to the right end of the heat-conducting pipe; a filter screen is provided inside the connecting pipe, and a cover plate is fixedly connected to the top of the connecting pipe by bolts; wherein, the outer surface of the filter screen is tightly fitted with the inner surface of the connecting pipe, and the end of the connecting pipe away from the boiler body is connected to the heat-conducting pipe; this boiler with waste heat recovery function facilitates the filtration and purification of flue gas, prevents internal blockage caused by long-term use, reduces environmental pollution, and improves the hot water heat energy conversion efficiency by stirring the water to be heated, thereby increasing the contact area between the water and the heat-conducting pipe.

[0004] The aforementioned technology discloses a boiler with waste heat recovery function. High-temperature flue gas is circulated from inside a heat exchange box through heat pipes to heat water, achieving the effect of heat exchange and waste heat utilization. A removable filter screen is installed on the connecting pipe before the flue gas enters the heat pipes to filter and intercept particulate impurities in the flue gas, preventing large amounts of particulate impurities from entering the heat pipes and causing blockages. However, the following shortcomings still exist in its use:

[0005] 1. During filtration, dust particles and impurities tend to accumulate and clog the filter screen, making it impossible to clean them simultaneously with filtration, thus hindering long-term, stable, and unobstructed filtration. 2. Utilizing the self-flowing of flue gas is problematic because the dust particles themselves have insufficient power, leading to smoke blockage at filtration and duct reversal points, making stable flow difficult. Therefore, this application proposes an electric boiler with waste heat recovery capabilities to address the aforementioned problems. Utility Model Content

[0006] The purpose of this invention is to provide an electric boiler with waste heat recovery function to solve the problems mentioned in the background art.

[0007] To achieve the above objectives, this utility model provides the following technical solution: an electric boiler with waste heat recovery function, comprising:

[0008] The top of the electric boiler body is connected to and fixed with a flue gas exhaust pipe.

[0009] The heat exchanger is filled with water.

[0010] The cylindrical box body has a connecting pipe fixed to the top left side of its top and the top of the flue gas exhaust pipe.

[0011] A circular rotating base is movably fitted inside a circular box. The top of the circular rotating base has multiple vent holes at equal intervals in a ring shape. Stainless steel filter screens are fixedly installed in the vent holes. The vent hole on the left side is vertically aligned and connected to one end of the connecting pipe. The connecting pipe is used to allow the high-temperature flue gas discharged from the boiler body to enter the vent hole on the left side. The stainless steel filter screen is used to filter and intercept dust particles and impurities in the flue gas.

[0012] The heat-conducting coil is located inside the heat exchange box, with one end embedded and fixed to the bottom of the circular box and vertically aligned with the vent on the left side; the heat-conducting coil is used for heat exchange between the filtered flue gas and the water to achieve water heating.

[0013] The rotary agitator is installed on the heat exchange box and fixedly connected to the bottom center of the rotary base. The rotary agitator is used to drive the rotary base to rotate and agitate the water as a whole, so that the water can be heated more evenly under agitation. The rotation of the rotary base drives multiple stainless steel filter screens to rotate, aligning them with the connecting pipes in sequence, and allowing the multiple stainless steel filter screens to be recycled in sequence.

[0014] The flue gas extraction, unblocking, and cleaning assembly is fixedly installed on the top of the heat exchange box and connected to the other end of the heat-conducting coil. The flue gas extraction, unblocking, and cleaning assembly is embedded and fixed on the bottom right side of the circular box and vertically aligned with the vent on the right side. The flue gas extraction, unblocking, and cleaning assembly is used to provide suction force to the flue gas through the heat-conducting coil and the vent on the left side, enhancing the entry effect of the flue gas and reducing the phenomenon that the flue gas is difficult to pass through the stainless steel filter screen by natural flow. It is also used to use the flue gas after filtration and heat exchange to circulate and back-flush multiple rotating stainless steel filters on the right side to clean and unblock them, ensuring the real-time unobstructed and stable effect of the stainless steel filters.

[0015] The slag discharge assembly is embedded and fixed on the top right side of the cylindrical box and vertically aligned with the vent on the right side; the slag discharge assembly is used to discharge and collect the impurities blown up during backflushing cleaning.

[0016] Preferably, the rotary agitation assembly includes a dual-shaft motor fixedly installed on the top of the heat exchange box. The output shaft at the bottom of the dual-shaft motor extends into the heat exchange box and is fixedly connected to a stirring shaft. Stirring blades are fixedly connected to both sides of the bottom of the stirring shaft. The stirring shaft is located inside the heat-conducting coil and does not contact it. The output shaft at the top of the dual-shaft motor is fixedly connected to the center of the bottom of the rotary base.

[0017] Preferably, the flue gas extraction and cleaning assembly includes an air pump fixedly installed on the top of the heat exchange box. A right-angle tube head is fixedly connected between the air inlet of the air pump and the other end of the heat conduction coil. A gas distribution box is fixedly connected to the air outlet of the air pump. The gas distribution box is embedded and fixedly installed on the bottom right side of the circular box. Multiple cleaning pipes are fixedly connected to the top of the gas distribution box. All multiple cleaning pipes are vertically aligned and connected to the vent on the right side.

[0018] Preferably, the slag discharge assembly includes an L-shaped tube embedded and fixed on the right side of the top of the cylindrical box. The bottom end of the L-shaped tube is configured as a cover structure. The outer side of the right end of the L-shaped tube is provided with an external thread and an internal threaded sleeve is threadedly connected to it. A breathable dust collection bag is connected and fixed to the right side of the internal threaded sleeve.

[0019] Preferably, four support rods are fixedly connected in a rectangle between the bottom of the circular box and the top of the heat exchange box, and the air pump is located between the two support rods on the right side.

[0020] Preferably, one end of the heat-conducting coil is configured as a funnel-shaped structure.

[0021] Preferably, a water inlet valve is fixedly connected to the top right side of the heat exchange box, a tap water supply pipe is fixedly connected to the right end of the water inlet valve, and a drain valve is fixedly connected to the bottom right side of the heat exchange box.

[0022] Compared with the prior art, the beneficial effects of this utility model are:

[0023] 1. Through the combination of the connecting pipe, circular box, heat exchange box, heat conduction coil, circular rotating seat, stainless steel filter screen and flue gas suction and cleaning components, it can filter and intercept the dust particles and impurities in the flue gas. By actively providing suction force through the air pump, it enhances the entry effect of the flue gas, reduces the phenomenon that the natural flow of flue gas is difficult to pass through the stainless steel filter screen or that smoke will be blocked, and improves the flow stability.

[0024] 2. Through the combination of the set circular rotating seat, stainless steel filter screen, vortex agitation component, flue gas suction and cleaning component and slag discharge component, multiple stainless steel filter screens can be used for cyclic filtration and at the same time for integrated cyclic backflushing cleaning and slag discharge. This prevents dust particles and impurities from accumulating and covering the surface of the stainless steel filter screen, causing blockage, ensuring long-term stable and smooth filtration, and improving the stability of filtration.

[0025] 3. In addition, the automatic discharge and collection of impurities using breathable dust collection bags is a convenient method. Since the dust particles are very small and take up very little space, they only need to be disassembled and replaced every few days or a long time. Furthermore, the breathable dust collection bags are located on the outside for easy disassembly and replacement, reducing the frequency of manual disassembly and handling and improving ease of use.

[0026] This invention, through a series of structures, can filter and intercept smoke particles and impurities in flue gas. By actively providing suction force through an air pump, it enhances the entry effect of flue gas, reduces the phenomenon of flue gas being unable to pass smoothly through the stainless steel filter screen or causing smoke blockage, improves flow stability, and facilitates the cyclical filtration and utilization of multiple stainless steel filter screens while simultaneously performing integrated cyclic backflushing for cleaning, unblocking, and slag removal. This prevents smoke particles and impurities from stagnating and accumulating on the surface of the stainless steel filter screen, causing blockage, ensuring long-term stable and smooth filtration, and improving filtration stability. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the structure of an electric boiler with waste heat recovery function proposed in this utility model.

[0028] Figure 2 This is a schematic diagram of the main sectional view of an electric boiler with waste heat recovery function proposed in this utility model.

[0029] Figure 3 for Figure 2 A magnified structural diagram of part A in the diagram;

[0030] Figure 4 This is a three-dimensional structural diagram of the connecting component between the rotary seat and the stainless steel filter screen of an electric boiler with waste heat recovery function proposed in this utility model.

[0031] In the diagram: 1. Electric boiler body; 2. Heat exchange box; 201. Water inlet valve; 202. Drain valve; 3. Circular box; 301. Connecting pipe; 302. Heat conduction coil; 4. Circular rotating seat; 401. Vent hole; 402. Stainless steel filter screen; 5. Dual-shaft motor; 501. Stirring shaft; 502. Stirring blade; 6. Air pump; 601. Air distribution box; 602. Cleaning pipe; 7. L-shaped pipe; 701. Breathable dust collection bag. Detailed Implementation

[0032] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0033] like Figures 1 to 4 As shown in this embodiment, an electric boiler with waste heat recovery function includes:

[0034] The electric boiler body 1 has a flue gas exhaust pipe fixedly connected to its top;

[0035] The heat exchange box 2 is filled with water. A water inlet valve 201 is fixedly connected to the top right side of the heat exchange box 2. A tap water supply pipe is fixedly connected to the right end of the water inlet valve 201. A drain valve 202 is fixedly connected to the bottom right side of the heat exchange box 2.

[0036] The circular box 3 has a connecting pipe 301 that is fixedly connected to the top left of the flue gas discharge pipe. The bottom of the circular box 3 and the top of the heat exchange box 2 are fixedly connected in a rectangle by four support rods.

[0037] The circular rotating base 4 is movably fitted inside the circular box 3. The top of the circular rotating base 4 has multiple vent holes 401 that are evenly spaced in a ring shape. A stainless steel filter screen 402 is fixedly installed inside the vent holes 401. The vent hole 401 on the left side is vertically aligned and connected to one end of the connecting pipe 301. The connecting pipe 301 is used to allow the high-temperature flue gas discharged from the boiler body 1 to enter the vent hole 401 on the left side. The stainless steel filter screen 402 is used to filter and intercept dust particles and impurities in the flue gas.

[0038] The heat-conducting coil 302 is located inside the heat exchange box 2, and one end of it is embedded and fixed to the bottom of the circular box 3, and is vertically aligned and connected to the vent 401 on the left side. One end of the heat-conducting coil 302 is set as a funnel-shaped structure. The heat-conducting coil 302 is used for the filtered flue gas to exchange heat with water, so as to realize the water heating application.

[0039] The rotary agitator is installed on the heat exchange box 2 and fixedly connected to the bottom center of the rotary seat 4. The rotary agitator is used to drive the rotary seat 4 to rotate and agitate the water in one piece, so that the water can be heated more evenly under agitation. The rotation of the rotary seat 4 drives multiple stainless steel filter screens 402 to rotate, aligning them with the connecting pipe 301 in sequence, and allowing the multiple stainless steel filter screens 402 to be recycled in sequence.

[0040] The flue gas extraction, unblocking, and cleaning assembly is fixedly installed on the top of the heat exchange box 2 and connected to the other end of the heat conduction coil 302. The flue gas extraction, unblocking, and cleaning assembly is embedded and fixed on the bottom right side of the circular box 3 and vertically aligned and connected to the vent 401 on the right side. The flue gas extraction, unblocking, and cleaning assembly is used to provide suction force to the flue gas through the heat conduction coil 302 and the vent 401 on the left side, enhance the entry effect of the flue gas, reduce the phenomenon that the flue gas is difficult to pass through the stainless steel filter 402 by natural flow, and is used to use the flue gas after filtration and heat exchange to circulate and back-blow the rotating stainless steel filter 402 on the right side to clean and unblock it, ensuring the real-time unobstructed and stable effect of the stainless steel filter 402.

[0041] The slag discharge assembly is embedded and fixed on the top right side of the cylindrical box 3 and vertically aligned with and connected to the vent 401 on the right side; the slag discharge assembly is used to discharge and collect the impurities blown up during backflushing cleaning.

[0042] Specifically, the rotary agitator assembly includes a dual-shaft motor 5 fixedly mounted on the top of the heat exchange box 2. The output shaft of the dual-shaft motor 5 extends into the heat exchange box 2 and is fixedly connected to a stirring shaft 501. A circular through-hole is provided on the top of the heat exchange box 2, and a first bearing is fixedly fitted inside the through-hole. The inner ring of the first bearing is fixedly fitted to the outer side of the output shaft at the bottom of the dual-shaft motor 5 for rotational support. A second bearing is fixedly connected to the inner wall of the bottom of the heat exchange box 2, and the inner ring of the second bearing is fixedly fitted to the outer side of the stirring shaft 501 to support the stirring shaft. The effect of rotating the 501 is that the stirring blades 502 are fixedly connected to both sides of the bottom of the stirring shaft 501. The stirring shaft 501 is located inside the heat conduction coil 302 and does not contact it. The output shaft at the top of the dual-shaft motor 5 is fixedly connected to the bottom center of the rotary seat 4. The dual-shaft motor 5, stirring blades 502 and stirring shaft 501 work together to drive the rotary seat 4 and stirring shaft 501 to rotate. The stirring shaft 501 drives the stirring blades 502 to rotate and stir the water, thus achieving the effect of driving the rotary seat 4 to rotate and stirring the water in one unit.

[0043] Furthermore, the flue gas extraction, unblocking, and cleaning assembly includes an air pump 6 fixedly installed on the top of the heat exchange box 2. The air pump 6 is located between two support rods on the right side. A right-angle tube head is fixedly connected between the air inlet of the air pump 6 and the other end of the heat conduction coil 302. A gas distribution box 601 is fixedly connected to the air outlet of the air pump 6. The gas distribution box 601 is embedded and fixedly installed on the bottom right side of the circular box 3. An embedding hole is opened on the bottom right side of the circular box 3 to be fixedly connected to the outside of the gas distribution box 601. Multiple cleaning pipes 602 are fixedly connected to the top of the gas distribution box 601. The multiple cleaning pipes 602 are vertically aligned and connected to the vent 401 on the right side. The air pump 6, right-angle tube head, gas distribution box 601, and cleaning pipes 602 work together to utilize air... Pump 6 provides suction to the flue gas through the heat-conducting coil 302 and the vent 401 on the left side, enhancing the entry effect of the flue gas and reducing the phenomenon that the flue gas is difficult to pass through the stainless steel filter screen 402 by natural flow. The pump 6 also supplies the suction gas into the gas distribution box 601, and the gas is then blown upward through multiple cleaning pipes 602 to clean and unblock the stainless steel filter screen 402 that has rotated to the right side. Under the action of multiple stainless steel filter screens 402 rotating synchronously, the effect of cyclic back-blowing and cleaning of multiple rotating stainless steel filter screens 402 is achieved, preventing impurities from accumulating on the stainless steel filter screens 402 and causing poor ventilation, and ensuring the real-time smooth and stable effect of the stainless steel filter screen 402.

[0044] Furthermore, the slag collection assembly includes an L-shaped tube 7 embedded and fixed on the top right side of the cylindrical box 3. The bottom end of the L-shaped tube 7 is set as a cover-shaped structure. The outer side of the right end of the L-shaped tube 7 is provided with an external thread and an internal threaded sleeve is threadedly connected to it. The right side of the internal threaded sleeve is connected and fixed to a breathable dust collection bag 701. The L-shaped tube 7, the internal threaded sleeve and the breathable dust collection bag 701 work together to guide the impurities blown upward during the cleaning process to the breathable dust collection bag 701. The gas passes through the breathable dust collection bag 701, achieving the effect of discharging and collecting the impurities blown up during the backflushing cleaning. Moreover, the dust particles are very small and occupy very little space. They only need to be disassembled and replaced once every few days or for a long time. The breathable dust collection bag 701 is located on the outside, which makes it easy to disassemble and replace directly, reducing the frequency of manual disassembly and replacement and improving the convenience of use.

[0045] The circular box 3 consists of a box with an open top and a sealing plate fixed to the top of the box. The bottom end of the L-shaped tube 7 and one end of the connecting tube 301 are both embedded and fixed to the top of the sealing plate. The bottom of the sealing plate is in contact with the top of the circular rotating seat 4.

[0046] The usage method of this embodiment is as follows: When using the electric boiler with waste heat recovery function, start the air pump 6 and the dual-shaft motor 5. When the air pump 6 starts, it provides suction force to the flue gas through the heat conduction coil 302, the left vent 401 and the connecting pipe 301 in sequence, so that the flue gas can quickly enter the left vent 401. The stainless steel filter 402 on the left side filters and intercepts the dust particles and impurities in the flue gas. The filtered gas is drawn into the heat conduction coil 302 and flows. Water absorbs the heat of the high temperature flue gas through the heat conduction coil 302, realizing the effect of heat exchange to heat the water, thereby realizing the effect of flue gas waste heat recovery. On-site personnel can use the heated water as needed. By actively providing suction force by the air pump 6, the entry effect of flue gas is enhanced, reducing the phenomenon that the flue gas is difficult to pass through the stainless steel filter 402 or is blocked by natural flow, and improving the flow stability.

[0047] When the dual-shaft motor 5 starts, it drives the rotary base 4 and the stirring shaft 501 to rotate. The stirring shaft 501 drives the stirring blades 502 to rotate, agitating the water and making the water heat up more evenly through agitation. The rotation of the rotary base 4 drives multiple stainless steel filter screens 402 to rotate, aligning them sequentially with the connecting pipes 301, thus allowing for the sequential recycling of multiple stainless steel filter screens 402. When the air pump 6 starts, the extracted gas is also transported upwards to the air distribution box 601, and then blown upwards through multiple cleaning pipes 602 to clean and unblock the stainless steel filter screens 402 that have rotated to the right. Under the synchronous rotation of multiple stainless steel filter screens 402, a cyclical backflushing cleaning and unblocking effect is achieved, blowing upwards... Impurities are guided outward through the L-shaped tube 7 to the breathable dust collection bag 701. The gas passes through the breathable dust collection bag 701, achieving the effect of circulating filtration of multiple stainless steel filter screens 402 while simultaneously circulating backflushing for cleaning, unblocking, and slag removal. This prevents dust particles from accumulating and clogging the surface of the stainless steel filter screens 402, ensuring long-term stable and smooth filtration and improving filtration stability. In addition, the automatic discharge and collection of impurities using the breathable dust collection bag 701 is convenient because dust particles are small and occupy very little space, requiring only a long time or several days for disassembly and replacement. Furthermore, the breathable dust collection bag 701 is located on the outside for easy direct disassembly and replacement, reducing the frequency of manual disassembly and improving ease of use.

[0048] Finally, it should be noted that the above description is merely a preferred embodiment of this utility model and is not intended to limit the utility model. Although the utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this utility model should be included within the protection scope of this utility model.

Claims

1. An electric boiler with waste heat recovery function, comprising an electric boiler body (1), characterized in that: include: The electric boiler body (1) has a flue gas exhaust pipe fixedly connected to its top; The heat exchange box (2) is filled with water. The cylindrical box (3) has a connecting pipe (301) fixed between its top left side and the top of the flue gas exhaust pipe; The circular rotating seat (4) is movably fitted inside the circular box (3). The top of the circular rotating seat (4) is provided with multiple vent holes (401) at equal intervals in a ring shape. A stainless steel filter screen (402) is fixedly installed inside the vent holes (401). The vent hole (401) on the left side is vertically aligned and connected to one end of the connecting pipe (301). The heat-conducting coil (302) is located inside the heat exchange box (2), and one end of it is embedded and fixed to the bottom of the circular box (3), and is vertically aligned and connected to the vent (401) on the left side. The rotary agitator assembly is installed on the heat exchange box (2) and fixedly connected to the bottom center of the rotary seat (4); The flue gas extraction and cleaning assembly is fixedly installed on the top of the heat exchange box (2) and connected to the other end of the heat conduction coil (302). The flue gas extraction and cleaning assembly is embedded and fixed on the bottom right side of the round box (3) and vertically aligned with the vent hole (401) on the right side. The slag collection assembly is installed and fixed on the top right side of the circular box (3) and vertically aligned with the vent (401) on the right side.

2. An electric boiler with waste heat recovery function according to claim 1, characterized in that: The rotary agitation assembly includes a dual-shaft motor (5) fixedly installed on the top of the heat exchange box (2). The output shaft of the dual-shaft motor (5) extends into the heat exchange box (2) and is fixedly connected to a stirring shaft (501). Stirring blades (502) are fixedly connected to both sides of the bottom of the stirring shaft (501). The stirring shaft (501) is located inside the heat conduction coil (302) and does not contact it. The output shaft at the top of the dual-shaft motor (5) is fixedly connected to the center of the bottom of the rotary seat (4).

3. An electric boiler with waste heat recovery function according to claim 1, characterized in that: The flue gas extraction and cleaning assembly includes an air pump (6) fixedly installed on the top of the heat exchange box (2). The air inlet of the air pump (6) is connected to the other end of the heat conduction coil (302) with a right-angle tube head. The air outlet of the air pump (6) is connected to a gas distribution box (601). The gas distribution box (601) is embedded and fixed on the bottom right side of the circular box (3). The top of the gas distribution box (601) is connected to multiple cleaning pipes (602). The multiple cleaning pipes (602) are vertically aligned and connected to the ventilation hole (401) on the right side.

4. An electric boiler with waste heat recovery function according to claim 1, characterized in that: The discharge slag collection assembly includes an L-shaped tube (7) embedded and fixed on the right side of the top of the circular box (3). The bottom end of the L-shaped tube (7) is set as a cover structure. The right side of the L-shaped tube (7) is provided with an external thread and an internal thread sleeve is threadedly connected. The right side of the internal thread sleeve is connected to and fixed with a breathable dust collection bag (701).

5. An electric boiler with waste heat recovery function according to claim 3, characterized in that: The bottom of the circular box (3) and the top of the heat exchange box (2) are fixedly connected in a rectangle by four support rods, and the air pump (6) is located between the two support rods on the right side.

6. An electric boiler with waste heat recovery function according to claim 1, characterized in that: One end of the heat-conducting coil (302) is configured as a funnel-shaped structure.

7. An electric boiler with waste heat recovery function according to claim 1, characterized in that: A water inlet valve (201) is fixedly connected to the top right side of the heat exchange box (2), and a tap water supply pipe is fixedly connected to the right end of the water inlet valve (201). A drain valve (202) is fixedly connected to the bottom right side of the heat exchange box (2).

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