Cooling and waste heat recovery method of sintered ore and pelletized ore and boiler thereof

Abstract

The present invention discloses a boiler for cooling and recovering waste heat of sintered ore and pelletized ore, comprising a solid-solid heat exchanger, wherein the solid-solid heat exchanger comprises a solid-solid heat exchanger startup protection device, a primary evaporator and a secondary evaporator; the solid-solid heat exchanger startup protection device comprises a protection device heating pipe, a superheated steam introduction pipe, a mixing header, an evaporation heating surface pipe outlet and an evaporation heating surface pipe inlet. The boiler of the present invention works stably when processing high-temperature materials, and no pipe bursts occur. Ordinary carbon steel pipes can be used to manufacture superheaters, which greatly reduces costs. A high-temperature circulation pump is also saved, reducing investment, energy consumption and failures. The present invention also discloses a method for cooling and recovering waste heat of sintered ore and pelletized ore. At the initial startup, high-temperature steam is introduced from a bypass into the startup protection device to first establish a circulation. The method of the present invention is simple, feasible, safe and reliable.

Description

Technical Field

[0001] The invention relates to the technical field of heat exchange equipment, and in particular to a device for protecting a solid-solid heat exchanger for sintered ore or pelletized ore when the solid-solid heat exchanger is started, and a boiler used for the device. Background Art

[0002] At present, the cooling process of high-temperature sintered ore and pelletized ore (hereinafter referred to as "high-temperature materials") in China mainly adopts belt air coolers, ring air coolers or vertical air cooling devices for cooling. The dust-containing hot flue gas used to cool the high-temperature materials then enters the waste heat boiler to produce hot water or low-parameter steam. The heat recovery system is complex, the air leakage rate is high, the sensible heat recovery efficiency of high-temperature materials is low, and the operation and maintenance costs are high.

[0003] In view of the above situation, a vertical solid heat exchange waste heat recovery device is now used to recover heat by allowing the high-temperature material to pass through the superheater, evaporator and economizer arranged from top to bottom in sequence to solve the above problems existing in the high-temperature material waste heat recovery system in the prior art.

[0004] The vertical solid heat exchange waste heat recovery device is an important part of the entire smelting process, and the safety, continuity and stability of its operation are crucial. Due to the solid-solid heat exchange of high-temperature materials: high material temperature, high heat flux density, high thermal conductivity and other characteristics, it is easy to cause the heating surface of the superheater that exchanges heat with it to be suddenly heated, the metal wall temperature of the local heating surface to overheat, the heating surface to be damaged, and the overall operation of the boiler to be affected.

[0005] Reference Figure 1 In order to improve the above problem, a solution of adding an evaporator before the superheater 2 is shown. The added evaporator is the primary evaporator 1, and the original evaporator is the secondary evaporator 4. The primary evaporator 1 and the secondary evaporator 4 are respectively provided with a primary evaporator outlet header 1b and a secondary evaporator outlet header 4a, which are respectively connected to the steam drum 5 through pipelines, and the liquid water in the steam drum 5 is respectively transported to the primary evaporator 1 and the secondary evaporator 4 through pipelines.

[0006] The inlet end of the economizer comes from the water supply operation console, and the outlet end is connected to the steam drum, and enters the primary evaporator 1 and the secondary evaporator 4 through the downcomer. The steam-water mixture generated after heating by the primary evaporator 1 and the secondary evaporator 4 enters the steam drum 5, and the saturated steam separated in the steam drum 5 enters the superheater 2 through the pipeline. The steam heated by the superheater 2 enters the steam network or steam turbine for power generation.

[0007] In this way, by adding a first-stage evaporator 1 in the area of ​​higher temperature field, steam can be generated as quickly as possible to protect the superheater 2; at the same time, the superheater 2 is arranged in the area of ​​lower temperature field, which can also well protect the superheater 2.

[0008] This existing conventional water circulation flow mode does not cause any problem for conventional boilers, but the water circulation is slow to establish and cannot be well adapted to waste heat recovery boilers in the specific environment of solid-solid heat exchange of high-temperature materials.

[0009] The above improved structure or such technical enlightenment appears in the following patents:

[0010] 1. High-temperature solid heat recovery waste heat boiler and waste heat recovery method, authorization announcement number CN 104048284 A, authorization announcement date 2014.09.17;

[0011] 2. Waste heat boiler with protective evaporator, authorization announcement number CN 206648007 U, authorization announcement date 2017.11.17;

[0012] 3. A waste heat boiler flue gas denitrification device, authorization announcement number CN 209549128 U, authorization announcement date 2019.10.29.

[0013] Unfortunately, the above improved structure still has some shortcomings. Taking a certain type of solid-solid heat exchange high-temperature waste heat recovery boiler adopting the improved structure as an example, the following problems are prone to occur:

[0014] The boiler starts up slowly, and the water circulation on the working medium side of the boiler is not easy to establish. The enthalpy of saturated water under normal pressure is 417kj / kg, the enthalpy of saturated steam is 2676kj / kg, and the latent heat of vaporization is 2259kj / kg. That is, to turn water into steam, a large amount of heat needs to be absorbed. According to the heat transfer coefficient of 55W / M2℃, it takes about 10 minutes to generate steam, and the water circulation is slowly established at this time. There is no problem for conventional boilers, but the establishment speed of water circulation is slow, and it cannot adapt well to the waste heat boiler in the specific environment of solid-solid heat exchange of high-temperature materials.

[0015] (2) Before the water circulation is established, the medium in the evaporator heat exchange tube is in a static state. Since the outside of the evaporator heat exchange tube is solid-solid heat exchange, the heat flux density is very large. For the evaporation heating surface of the evaporator heat exchange tube, its heat load is greater than 6*10^6W / m2, so film boiling occurs, resulting in an increase in the temperature of the evaporation heating surface tube wall and a tube burst accident. For the superheater heating surface, since the water circulation is not established, there is no steam circulation cooling in the superheater heat exchange surface tube, the heat flux density outside the tube is large, and there is no medium cooling it in the tube, which can easily cause the tube wall temperature to rise to more than 650°C. It is difficult for us to find heat exchange surface tubes that can adapt to this temperature. Even if we can find it, it will be very expensive.

[0016] (3) To overcome problems (1) and (2), a hot water circulation pump is used for forced circulation, which increases power consumption. At the same time, equipment failure will cause water circulation stagnation, thus causing a pipe burst accident. Summary of the invention

[0017] The technical problem to be solved by the present invention is that when the existing solid-solid heat exchange high-temperature waste heat recovery boiler processes high-temperature materials:

[0018] Slow start-up due to slow water circulation;

[0019] It is more prone to pipe bursting accidents, and the material has high requirements for heat resistance. It is difficult to find suitable materials or the cost is very high;

[0020] The use of hot water circulation pumps for forced circulation increases power consumption. At the same time, equipment failure will cause water circulation stagnation, which may lead to pipe burst accidents.

[0021] In order to achieve the above-mentioned object of the invention, the technical solution adopted by the present invention is:

[0022] Provided is a cooling and waste heat recovery boiler for sintered ore and pelletized ore, which is a solid-solid heat exchange high-temperature waste heat recovery boiler, characterized in that it comprises a solid-solid heat exchanger, the solid-solid heat exchanger comprises a solid-solid heat exchanger startup protection device, a primary evaporator and a secondary evaporator;

[0023] The inlet of the first-stage evaporator is connected to the outlet of the evaporation heating surface tube of the solid-solid heat exchanger startup protection device, and the outlet of the second-stage evaporator is connected to the inlet of the evaporation heating surface tube of the solid-solid heat exchanger startup protection device;

[0024] The solid-solid heat exchanger startup protection device comprises a protection device heating pipe, a superheated steam introduction pipe, a mixing header, an evaporation heating surface pipe outlet and an evaporation heating surface pipe inlet;

[0025] The protection device heating tube is arranged in the mixing header, one end of the protection device heating tube is connected to the superheated steam inlet pipe outside the mixing header, and at least one small hole for discharging steam is arranged on the protection device heating tube; the mixing header is provided with an evaporation heating surface tube outlet and an evaporation heating surface tube inlet, the evaporation heating surface tube outlet is arranged above the mixing header, and the evaporation heating surface tube inlet is arranged below the mixing header.

[0026] Furthermore, there are a plurality of small holes, which are evenly and densely distributed on the heating tube of the protection device.

[0027] Furthermore, the mixing header of the solid-solid heat exchanger startup protection device replaces the first-stage evaporator outlet header of the first-stage evaporator and the second-stage evaporator outlet header of the second-stage evaporator; the heating tube inlet of the first-stage evaporator is connected to the evaporation heating surface tube outlet; the heating tube outlet of the second-stage evaporator is connected to the evaporation heating surface tube inlet.

[0028] The present invention also provides a method for cooling and recovering waste heat of sintered ore and pelletized ore, and the specific steps are as follows:

[0029] Step 1: At the initial start-up, high-temperature steam is introduced from the side and enters the mixing header through the superheated steam introduction pipe and the protective device heating pipe. After the high-temperature steam enters the protective device heating pipe, it is sprayed into the mixing header through the small hole, mixed with the water in the mixing header, and releases heat to heat the water in the mixing header to generate steam;

[0030] Step 2: Steam enters the primary evaporator from the outlet of the evaporation heating surface tube, and forms a self-heating cycle due to the density difference between water and steam. At the same time, after the steam enters the steam drum 5 for separation, it enters the superheater 2, thus forming a complete cycle. After that, the high-temperature material enters the waste heat recovery boiler;

[0031] Step 3: After the high-temperature material contacts the solid-solid heat exchanger and the water circulation of the solid-solid heat exchanger can continue through the high-temperature material, stop introducing the high-temperature steam;

[0032] Step 4: After the high-temperature material passes through the solid-solid heat exchanger and superheater, it continues to pass downward through the economizer and the material discharge device to complete the cooling of the sintered ore and pelletized ore and the waste heat recovery.

[0033] The beneficial effects of the present invention are:

[0034] When the solid-solid heat exchanger is used for cooling sintered ore and pelletized ore, or for waste heat recovery boilers, and when processing high-temperature materials, the solid-solid heat exchanger works stably, effectively establishing water circulation before starting the solid-solid heat exchanger, thereby protecting the solid-solid heat exchanger from tube bursting. At the same time, the superheater temperature is greatly reduced, and ordinary carbon steel pipe manufacturing materials can be used, which greatly reduces costs. It also saves high-temperature circulation pumps, reduces investment, reduces energy consumption, and reduces mechanical failure points.

[0035] The method for cooling sintered ore and pelletized ore and recovering waste heat by using the cooling and waste heat recovery boiler is simple, feasible, safe and reliable. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a partial structural schematic diagram of an existing solid-solid heat exchange high-temperature waste heat recovery boiler, in which only the primary evaporator 1, the primary evaporator outlet header 1b, the superheater 2, the secondary evaporator 4, the secondary evaporator outlet header 4a, the steam drum 5 and the hot water circulation pump 6 related to the present invention are shown;

[0037] Figure 2 It is a structural schematic diagram of the solid-solid heat exchanger startup protection device;

[0038] Figure 3is a structural schematic diagram of a solid-solid heat exchanger, and the solid-solid heat exchanger adopts the solid-solid heat exchanger startup protection device;

[0039] Figure 4 It is a cooling and waste heat recovery boiler for sintered ore and pelletized ore, and is a solid-solid heat exchange high-temperature waste heat recovery boiler. The waste heat recovery boiler uses the solid-solid heat exchanger as the primary evaporator 1 and the secondary evaporator 4; the contents not related to the present invention are omitted in the figure;

[0040] Among them, the first-stage evaporator 1, the first-stage evaporator outlet header 1b, the superheater 2,

[0041] Start protection device 3, protection device heating pipe 3a, superheated steam introduction pipe 3b, mixing header 3c, evaporation heating surface pipe outlet 3e, evaporation heating surface pipe inlet 3f,

[0042] Secondary evaporator 4, secondary evaporator outlet header 4a, steam drum 5, hot water circulation pump 6. DETAILED DESCRIPTION

[0043] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments. Examples of the embodiments are shown in the accompanying drawings, and the embodiments described with reference to the accompanying drawings are only exemplary and are only used to explain the present invention, rather than limiting the present invention.

[0044] The directions and positional relationships indicated by the terms "front", "rear", "left", "right", etc. described in the present invention are based on the directions and positional relationships shown in the accompanying drawings and are only for the convenience and simplification of description. They do not indicate or imply a specific orientation that the device or original referred to must have, nor can they be understood as limitations on the present invention.

[0045] In order to explain the present invention more conveniently and clearly, the specific embodiments will be explained in sequence in the hierarchy of "solid-solid heat exchanger start-up protection device" → "solid-solid heat exchanger" → "cooling of sintered ore and pelletized ore, waste heat recovery boiler".

[0046] 1. Solid-solid heat exchanger startup protection device and its use method

[0047] like Figure 2 As shown, the solid-solid heat exchanger startup protection device includes a protection device heating pipe 3a, a superheated steam introduction pipe 3b, a mixing header 3c, an evaporation heating surface pipe outlet 3e and an evaporation heating surface pipe inlet 3f;

[0048] The protection device heating pipe 3a is arranged in the mixing header 3c, one end of the protection device heating pipe 3a is connected to the superheated steam introduction pipe 3b outside the mixing header 3c, and a plurality of small holes for discharging steam are evenly distributed on the protection device heating pipe 3a.

[0049] It is understandable that, as a reasonable extension, the small holes do not have to be arranged evenly and / or densely. The purpose of arranging the small holes evenly and densely is to heat the water in the mixing header 3c as efficiently as possible, so that it can generate more steam as quickly as possible.

[0050] The mixing header 3c is provided with an evaporation heating surface tube outlet 3e and an evaporation heating surface tube inlet 3f. The evaporation heating surface tube outlet 3e is provided above the mixing header 3c, and the evaporation heating surface tube inlet 3f is provided below the mixing header 3c.

[0051] In this embodiment, the evaporation heating surface pipe outlet 3e is used to connect to the inlet of the primary evaporator 1. The evaporation heating surface pipe inlet 3f is used to connect to the outlet of the secondary evaporator 4. In Embodiment 2, the solid-solid heat exchanger using this will be described in detail.

[0052] After the solid-solid heat exchanger is provided with the solid-solid heat exchanger startup protection device, the solid-solid heat exchanger and the superheater serving as the evaporator can be well protected when the waste heat recovery boiler is started.

[0053] The solid-solid heat exchanger startup protection device is implemented as follows: a stream of steam is drawn from the side and enters the solid-solid heat exchanger startup protection device to heat the existing evaporator water to generate steam, thereby accelerating the establishment of water circulation. In this way, the evaporator and superheater will be well protected at the initial startup.

[0054] Specific working principle: At the initial start-up, high-temperature steam is introduced from the side and enters the mixing header 3c through the superheated steam introduction pipe 3b and the protection device heating pipe 3a. After the high-temperature steam enters the protection device heating pipe 3a, it is sprayed into the mixing header through the small hole, mixed with the water in the mixing header, and releases heat to heat the water in the mixing header to generate steam.

[0055] Because the solid-solid heat exchanger startup protection device will be set on the circulation loop of the solid-solid heat exchanger as the first-stage evaporator 1 and the second-stage evaporator 4 in actual application, the steam enters the first-stage evaporator 1 from the evaporation heating surface pipe outlet 3e, and forms a self-heating cycle due to the density difference between water and steam. At the same time, the steam enters the steam drum 5 for separation and then enters the superheater 2, thus forming a complete cycle. After that, the high-temperature material enters the waste heat recovery boiler. Then, after the high-temperature material contacts the solid-solid heat exchanger and can continue the water circulation of the solid-solid heat exchanger through the high-temperature material, the high-temperature steam is stopped.

[0056] Since a complete water cycle has been established at the beginning of the waste heat recovery boiler startup, all heating surfaces can be well cooled, and after adding high-temperature materials, all heating surfaces can operate normally, thus playing a good protective role.

[0057] Similarly, take a certain type of solid-solid heat exchange high-temperature waste heat recovery boiler described in the background technology as an example. Due to the establishment of the cycle, the evaporator's evaporation heating surface will be well cooled due to the flow of the medium in the tube, and the heat load of the evaporator's evaporation heating surface will also be greatly reduced, about 3*10^5 W / m2, which will not cause the generation of film boiling, thereby well protecting the evaporator's evaporation heating surface tube; for the superheater 2 heating surface, even if there is a large heat flux density outside the tube, due to the flow of steam in the superheater tube, the heating surface of the tube is well cooled, and its metal wall temperature is greatly reduced to below 400°C. In this way, we can meet the use requirements by choosing ordinary carbon steel pipes, and the material and cost are greatly reduced.

[0058] We can use natural circulation to meet the requirements of high-temperature solid particle solid-solid heat exchange waste heat recovery device. In this way, we can save the high-temperature circulation pump. Not only can we reduce investment and energy consumption, but also reduce mechanical failure points.

[0059] 2. Solid-solid heat exchanger

[0060] The present invention also provides a solid-solid heat exchanger, including a primary evaporator 1 and a secondary evaporator 4, and adopts the solid-solid heat exchanger startup protection device as described in Example 1, the inlet of the primary evaporator 1 is connected to the evaporation heating surface tube outlet 3e of the solid-solid heat exchanger startup protection device, and the outlet of the secondary evaporator 4 is connected to the evaporation heating surface tube inlet 3f of the solid-solid heat exchanger startup protection device.

[0061] like Figure 3 As shown, an example of a solid-solid heat exchanger using a solid-solid heat exchanger startup protection device is described in detail.

[0062] In this example, the mixing manifold 3c of the solid-solid heat exchanger startup protection device replaces the first-stage evaporator outlet manifold 1b of the first-stage evaporator 1 and the second-stage evaporator outlet manifold 4a of the second-stage evaporator 4, and each heating tube inlet of the first-stage evaporator 1 is connected to the evaporation heating surface tube outlet 3e; each heating tube outlet of the second-stage evaporator 4 is connected to the evaporation heating surface tube inlet 3f.

[0063] During the circulation, the water in the drum 5 first enters the secondary evaporator 4, and then enters the mixing header 3c after passing through the solid-solid heat exchanger startup protection device.

[0064] It is reasonable to speculate that as a solid-solid heat exchanger startup protection device, more applications are as follows: the solid-solid heat exchanger startup protection device can be applied to a certain stage of evaporator alone, instead of connecting two stages of evaporators at the same time, but connecting the two stages of evaporators in series.

[0065] The working principle and beneficial effects of the solid-solid heat exchanger, including the working principle and beneficial effects of the solid-solid heat exchanger startup protection device, have been explained in Example 1 and will not be repeated here.

[0066] 3. Cooling and waste heat recovery boilers for sintered ore and pelletized ore, and methods for cooling and waste heat recovery for sintered ore and pelletized ore

[0067] like Figure 4 As shown, the present invention also provides a cooling and waste heat recovery boiler for sintered ore and pelletized ore, which is a solid-solid heat exchange high-temperature waste heat recovery boiler. The cooling and waste heat recovery boiler for sintered ore and pelletized ore adopts the solid-solid heat exchanger described in Example 2 as the primary evaporator 1 and the secondary evaporator 4.

[0068] A superheater 2 is provided between the primary evaporator 1 and the secondary evaporator 4, and an economizer is provided below the secondary evaporator 4. The inlet of the superheater 2 is connected to the outlet at the top of the drum 5, and the inlet of the superheater 2 is connected to the steam pipe network. The inlet of the economizer is connected to the bottom of the drum 5, and the outlet of the economizer is connected to the upper part of the drum 5.

[0069] The present invention also provides a method for cooling and recovering waste heat of sintered ore and pelletized ore, using the cooling and waste heat boiler of sintered ore and pelletized ore, and the specific steps are as follows:

[0070] Step 1: At the initial start-up, high-temperature steam is introduced from the side and enters the mixing header 3c through the superheated steam introduction pipe 3b and the protection device heating pipe 3a. After the high-temperature steam enters the protection device heating pipe 3a, it is sprayed into the mixing header through the small hole, mixed with the water in the mixing header, and releases heat to heat the water in the mixing header to generate steam;

[0071] Step 2: Steam enters the primary evaporator 1 from the evaporation heating surface pipe outlet 3e, and forms a self-heating cycle due to the density difference between water and steam. At the same time, after the steam enters the steam drum 5 for separation, it enters the superheater 2, thus forming a complete cycle. After that, the high-temperature material enters the waste heat recovery boiler;

[0072] Step 3: After the high-temperature material contacts the solid-solid heat exchanger and the water circulation of the solid-solid heat exchanger can continue through the high-temperature material, stop introducing the high-temperature steam;

[0073] Step 4: After the high-temperature material passes through the solid-solid heat exchanger and the superheater 2, it continues downward through the economizer and the material discharge device to complete the cooling of the sintered ore and the pelletized ore and the waste heat recovery.

[0074] The working principle and beneficial effects of the cooling of the sintered ore and pelletized ore and the waste heat recovery boiler, including the working principle and beneficial effects of the solid-solid heat exchanger startup protection device, have been explained in Example 1 and will not be repeated again.

[0075] The specification and drawings of the present invention are considered to be illustrative rather than restrictive. On the basis of the present invention, those skilled in the art can make some substitutions and modifications to some of the technical features in accordance with the disclosed technical content without creative labor, all of which are within the protection scope of the present invention.

Claims

1. The cooling and waste heat recovery boiler for sintered ore and pelletized ore is a solid-solid heat exchange high-temperature waste heat recovery boiler, characterized in that: The invention comprises a solid-solid heat exchanger, wherein the solid-solid heat exchanger comprises a solid-solid heat exchanger startup protection device, a primary evaporator (1) and a secondary evaporator (4); The inlet of the first-stage evaporator (1) is connected to the outlet (3e) of the evaporation heating surface tube of the solid-solid heat exchanger startup protection device, and the outlet of the second-stage evaporator (4) is connected to the inlet (3f) of the evaporation heating surface tube of the solid-solid heat exchanger startup protection device; The solid-solid heat exchanger startup protection device comprises a protection device heating pipe (3a), a superheated steam introduction pipe (3b), a mixing header (3c), an evaporation heating surface pipe outlet (3e) and an evaporation heating surface pipe inlet (3f); The protection device heating pipe (3a) is arranged in the mixing header (3c), one end of the protection device heating pipe (3a) is connected to the superheated steam introduction pipe (3b) outside the mixing header (3c), and at least one small hole for discharging steam is arranged on the protection device heating pipe (3a); the mixing header (3c) is provided with an evaporation heating surface pipe outlet (3e) and an evaporation heating surface pipe inlet (3f), the evaporation heating surface pipe outlet (3e) is arranged above the mixing header (3c), and the evaporation heating surface pipe inlet (3f) is arranged below the mixing header (3c).

2. The sintered ore and pelletized ore cooling and waste heat recovery boiler according to claim 1, characterized in that: There are a plurality of small holes, which are evenly and densely distributed on the protective device heating tube (3a).

3. The cooling and waste heat recovery boiler for sintered ore and pelletized ore according to claim 1 or 2, characterized in that: The mixing header (3c) of the solid-solid heat exchanger startup protection device replaces the primary evaporator outlet header (1b) of the primary evaporator (1) and the secondary evaporator outlet header (4a) of the secondary evaporator (4); each heating tube inlet of the primary evaporator (1) is connected to the evaporation heating surface tube outlet (3e); and each heating tube outlet of the secondary evaporator (4) is connected to the evaporation heating surface tube inlet (3f).

4. A method for cooling and recovering waste heat of sintered ore and pelletized ore, characterized in that: The cooling and waste heat boiler of sintered ore and pelletized ore as claimed in any one of claims 1 to 3 is adopted, and the specific steps are as follows: Step 1: At the initial start-up, high-temperature steam is introduced from the side and enters the mixing header (3c) through the superheated steam introduction pipe (3b) and the protection device heating pipe (3a). After the high-temperature steam enters the protection device heating pipe (3a), it is sprayed into the mixing header through the small hole, mixed with the water in the mixing header, and releases heat to heat the water in the mixing header to generate steam; Step 2: Steam enters the primary evaporator (1) from the outlet of the evaporation heating surface tube (3e), and forms an autothermal cycle due to the density difference between water and steam. At the same time, after the steam enters the steam drum (5) for separation, it enters the superheater (2), thus forming a complete cycle. After that, the high-temperature material enters the waste heat recovery boiler; Step 3: After the high-temperature material contacts the solid-solid heat exchanger and the water circulation of the solid-solid heat exchanger can continue through the high-temperature material, stop introducing the high-temperature steam; Step 4: After the high-temperature material passes through the solid-solid heat exchanger and the superheater (2), it continues downward through the economizer and the material discharge device to complete the cooling of the sintered ore and pelletized ore and the waste heat recovery.

Images