CN203083359U - Natural gas heat accumulating type cupola - Google Patents

Abstract

The utility model relates to the field of cast iron smelting, in particular to a natural gas regenerative iron melting furnace, which solves the problems that the existing iron melting furnace cannot obtain high temperature, high-quality molten iron, and serious oxidation and burning of elements in the molten iron, including forehearth, The rear furnace and the fore furnace include a combustion chamber, a molten pool, and a bridge. The two sides of the molten pool are respectively provided with slag outlets. The natural gas transmission pipeline and air supply pipeline connected with it; the rear furnace includes the furnace body, the feeding port, and the flue gas discharge port. The air pipeline is connected, the gas inlet is connected with the natural gas transmission pipeline, there is a pulverized coal secondary air and a combustion-supporting secondary air structure in the middle of the furnace body, and the tubular heat exchanger is installed above the feeding port. The structure is compact and reasonable, the furnace operation is stable, and the energy saving effect Significantly, the burning loss rate of elements is low, greatly reducing CO2, NOx, SO2 emissions, and has a wide range of applications.

Description

Natural gas regenerative iron furnace

technical field

The utility model relates to the field of cast iron smelting, in particular to a natural gas heat storage type iron melting furnace.

Background technique

The most commonly used equipment for smelting cast iron is a coke-fired cupola. With the development of production, the demand contradiction of coke has become increasingly prominent, and people began to seek coke-substituting equipment for smelting cast iron according to their respective fuel resources.

It is well known that natural gas is not only an energy source with a high calorific value, but also emits the least amount of SOx, NOx, and CO after combustion. It also has the advantages of easy automatic control and convenient operation, so it is considered as a green, environmentally friendly, clean energy. Therefore, using natural gas as fuel and smelting cast iron has also attracted people's attention. Since the 1970s, my country has designed and applied coal pulverized iron furnaces, heavy oil furnaces, and natural gas furnaces to replace coke smelting equipment, and has also conducted systematic experimental research on its smelting principles and production processes. Some production experience and theoretical results. However, due to various reasons, there has not been a complete theory and finalized products for the natural gas furnace, especially for the rational combustion of the furnace structure, the superheating of molten iron, the control of chemical composition, the oxidation and burning loss of elements, and the reasonable structural design. There are no mature reports on the key issues, and no mature natural gas iron furnaces with mature technology applied in actual production. The inventor conducted long-term experimental research on the natural gas iron furnace, especially on the combustion characteristics of natural gas, the thermal principle and metallurgical principle of the iron furnace, how to overheat the molten iron, the strengthening of heat exchange, and the oxidation and combustion of various elements in the molten iron. After an in-depth discussion, it is believed that the key points in designing and manufacturing natural gas-fueled iron furnaces are how to obtain high-temperature and high-quality molten iron; how to control and reduce the oxidation and burning loss of various elements in molten iron; how to reduce CO2, SO2, and NOX combustion emissions. Therefore urgently need to develop a kind of furnace that can effectively solve above-mentioned many problems.

Contents of the invention

The utility model provides a natural gas heat storage type iron furnace in order to solve the existing problems that the existing iron furnace cannot obtain high temperature, high-quality molten iron, serious oxidation and burning of elements in the molten iron, and pollution of the environment by combustion emissions.

The utility model is realized by adopting the following technical scheme: the natural gas regenerative iron furnace includes a fore furnace and a rear furnace, the fore furnace and the rear furnace are connected through a burner port, the fore furnace includes a combustion chamber, and a melting furnace located at the bottom of the combustion chamber There are slag outlets on both sides of the molten pool, a shallow molten pool on the bridge surface, and slag discharge grooves at the arch angles on both sides of the bridge. The slag ditch is connected with the slag outlets on both sides of the molten pool of the fore furnace, and the combustion chamber is respectively connected with the natural gas delivery pipe and the air supply pipe connected with it; The flue gas discharge port, the bottom of the furnace body is provided with a raised furnace bottom, and an annular fire passage is formed between the raised furnace bottom and the inner wall of the furnace, and the annular fire passage communicates with the fire mouth. An air single preheating regenerative burner unit combination is installed, the flue gas outlet and air inlet of the burner are respectively connected with the air supply pipeline, and the gas inlet of the burner is connected with the natural gas transmission pipeline. The air single preheating regenerative burner unit combination is a known product, its structure and working principle are well known to those skilled in the art, and its number can be determined according to the size of the furnace body and actual needs.

A tubular heat exchanger is installed on the rear furnace body and above the feeding port, and the hot air outlets on both sides of the tubular heat exchanger communicate with the melting zone of the rear furnace body through the combustion-supporting secondary air pipe I respectively, wherein A hot air port communicates with the air supply duct through the combustion-supporting secondary air duct II. The tube heat exchanger uses the residual heat of the furnace gas to preheat the combustion air to 100-150°C, one way passes through the combustion secondary air pipe II for the single preheating regenerative burner, and the other passes through the combustion air secondary air pipe I Sending combustion-supporting secondary air above the melting zone of the furnace body can reduce the chemical heat loss taken away by the furnace gas, improve the thermal efficiency of the furnace, save fuel, and strengthen the heat exchange in the preheating zone.

The side wall of the annular fire passage is provided with an air delivery pipe with one end connected to the annular fire passage and the other end connected to the combustion-supporting secondary air pipe I. The air delivery pipe is provided with a pulverized coal storage funnel connected with it, and the pulverized coal storage funnel is The screw conveyor driven by the power mechanism is installed, and the pressure balance pipe connected to the air conveying pipe is installed on the upper side of the pulverized coal storage funnel. The design of this structure is an important means to strengthen the heat exchange in the melting zone, that is, the pipe heat exchange Combustion-supporting air and coal powder preheated to 100-150°C are fed into the burner together, which increases the temperature of the furnace gas, increases the expansion of the furnace gas, accelerates the airflow speed, increases convective heat transfer, saves fuel, and improves The thermal efficiency and melting rate are improved, and the furnace gas atmosphere can be reduced or weakly oxidized at the same time, and the burning loss of elements is greatly reduced.

An injector and an annular pipe are provided at the connection between the annular fire passage and the air delivery pipe, so that the coal powder entering the annular fire passage is evenly sprayed into the fire passage in a certain area, and the combustion efficiency is higher.

The flue gas discharge port on the top of the rear furnace body is connected to the bag dust removal device. The bag dust removal device is an existing known structure, which is used to deal with the emission of smoke and dust, and purify smaller dust, which meets the requirements of the relevant national industrial furnaces and kilns. emission standard requirements.

A siphon-type slag-separating chamber is set up in front of the burner to remove the slag flowing from the annular flue to the bridge, which is the first slag discharge. The molten iron flowing out of the siphon-type slag-separating chamber then enters the bottom of the bridge with a large area The shallow molten pool with a depth of about 50mm and a slope of 1:40 is used for the second slag discharge, and a slag discharge ditch and a slag discharge port are built on both sides of the shallow molten pool and at the arch angle of the bridge to discharge the slag from the siphon type slag discharge chamber. The molten slag and the slag covering the bridge shallow molten pool are discharged out of the furnace through the slag discharge ditch. As a result, the radiation convective heat transfer of the furnace gas and the furnace wall to the molten metal is increased, and the heated area of the molten metal surface is also increased.

The two sides of the bridge deck are staggered with curved retaining walls, which can properly increase the time for the molten metal to flow through the bridge in the case of a short bridge, so as to enhance the radiation convection heat transfer of the molten metal.

Based on the analysis of the thermal engineering and metallurgical principles of the natural gas regenerative iron furnace, the applicant has adopted the following specific implementation on the key issues of how to obtain high-temperature, high-quality molten iron and how to control and reduce the oxidation and burning loss of elements in molten iron Measures: Mainly apply the new combustion technology of regenerative high-temperature air low-oxygen combustion (High Temperature Air Combustion referred to as HTAC technology), add natural gas air single preheating regenerative burner unit combined combustion system on the front furnace body, and The forehearth, combustion chamber, bridge, rear furnace and other structures are ingeniously combined into a natural gas regenerative iron furnace, which not only achieves high efficiency and energy saving, obtains high-temperature molten iron, reduces element oxidation and burning loss, but also greatly reduces CO and CO ₂ and other greenhouse gas emissions, due to the high-temperature, low-oxygen combustion environment and the mixing effect of flue gas backflow, the generation of N _X is inhibited, and the emission of N _X can be greatly reduced (it can be reduced to below 100mg/m ³ ), The high-temperature environment also suppresses the generation of dioxins. Due to the rapid cooling of the exhaust gas, the resynthesis of dioxins is effectively prevented, so the emission of dioxins is also greatly reduced; at the same time, the following measures are taken to strengthen the heat exchange in the three zones Measures, one is to add a tubular heat exchanger to strengthen the heat exchange in the preheating zone and use the waste heat of the furnace gas to preheat the combustion air to 100-150 °C, one way is used for the regenerative combustion system, and the other way is through the combustion secondary air duct Ⅰ is fed above the melting zone of the furnace body; the second is in the melting zone, since the heat from the furnace gas to the metal charge is mainly convective heat transfer, the melting point of the metal charge is affected by the melting point of the metal, the chemical composition, the lumpiness of the charge, etc. Therefore, improving the heat exchange in the melting zone should first reduce the size of the material block and increase the heat transfer area of the furnace material to accelerate the melting process; the third is to increase the secondary air supply structure of pulverized coal, increase the temperature of the furnace gas, and increase the furnace temperature. The gas expands, accelerates the airflow speed, increases convective heat transfer, saves fuel, improves thermal efficiency and melting rate, and improves the furnace gas atmosphere, which can be reduced or weakly oxidized, and the burning loss of elements is greatly reduced; in addition, this utility model The bottom structure of the new natural gas regenerative iron furnace is designed as an inverted pot, and an annular fire channel is formed on the rear furnace wall. A siphon type slag discharge chamber is built between the bridge and the burner to remove the flow from the annular fire channel to the For the slag crossing the bridge, as the first slag discharge, the molten iron flowing out of the siphon slag discharge chamber then enters the bottom of the bridge, with a large area of shallow molten pool with a depth of about 50mm and a slope of 1:40, and in the shallow molten pool The slag discharge ditch and the slag discharge port are built on both sides and at the arch angle of the bridge, and the slag discharged from the siphon slag discharge chamber and the slag covering the shallow melting pool of the bridge are discharged out of the furnace through the slag discharge ditch, thereby increasing the Furnace gas and furnace wall radiate and convect heat to molten metal, and also increase the heated area of molten metal.

In short, in order to reduce and control the oxidative burning loss of elements, the inventor adopts high-temperature air, low-oxygen combustion technology and pulverized coal secondary air to control the atmosphere of the furnace gas (reducing or weakly oxidized) and adopts two-time slag separation technology to remove slag After measures such as oxides in the furnace, the oxidation and burning loss of C, Si, and Mn are greatly reduced. The utility model has compact and reasonable structure, advanced technology, stable furnace operation, and can meet the requirements of casting various iron castings. It is comparable to the use of coke. Compared with the fuel cupola, the energy-saving effect is remarkable, the element burning rate is low, and the emission of CO2 to the atmosphere is reduced by more than 30%. NOx and SO2 are also greatly reduced, which is suitable for small and medium-sized foundry enterprises with natural gas resources, especially for smelting low-carbon, low-sulfur and high-quality iron castings.

Description of drawings

Fig. 1 is the structural representation of the utility model;

Figure 2 is a working principle diagram of the air single preheating regenerative burner unit combination;

Fig. 3 is a structural schematic diagram of the air single preheating regenerative burner unit combination;

Fig. 4 is the top view of Fig. 3;

Fig. 5 is a schematic diagram of the pulverized coal secondary air structure;

Fig. 6 is the structural representation of bridge and front furnace, back furnace;

In the figure: 1-fore furnace; 2-back furnace; 3-crater; 4-combustion chamber; 5-melting pool; 6-bridge; 7-slag outlet; 10-natural gas transmission pipeline; 11-air supply pipeline; 12-furnace body; 13-feeding port; 14-flue gas discharge port; 15-raised furnace bottom; Thermal burner unit combination; 18-flue gas outlet; 19-air inlet; 20-gas inlet; 21-tube heat exchanger; 22-combustion secondary air duct Ⅰ; 23-combustion secondary air duct Ⅱ; 24 -air delivery pipe; 25-coal powder storage funnel; 26-screw conveyor; 27-pressure balance pipe; 28-injector; 29-ring pipe; 30-bag dust removal device; 31-curve retaining wall; 33-regenerator; 34-four-way reversing valve; 35-blower; 36-induced fan; 37-regenerator; 38-burner nozzle; 39-control valve.

Detailed ways

The natural gas regenerative iron furnace, as shown in Figure 1, includes a forehearth 1 and a rear furnace 2, the forehearth and the rear furnace are connected through the burner 3, the forehearth includes a combustion chamber 4, and a molten pool opened at the bottom of the combustion chamber 5 and the bridge 6 located between the molten pool and the crater, the two sides of the molten pool are respectively provided with slag outlets 7, the shallow molten pool 8 is opened on the bridge surface, and the slag discharge outlets are respectively provided at the arch angles on both sides of the bridge. Ditch 9, the slag discharge ditch is connected with the slag discharge outlets on both sides of the fore furnace molten pool, and the combustion chamber is respectively connected with the natural gas delivery pipeline 10 and the air supply pipeline 11; Port 13, the top of the furnace body is provided with a flue gas discharge port 14, and the flue gas discharge port 14 on the top of the rear furnace body 12 is connected to the bag dust removal device 30; the bottom of the furnace body is provided with a raised furnace bottom 15, and the raised furnace bottom An annular fire channel 16 is formed between the inner wall of the furnace, and the annular fire channel communicates with the burner, as shown in Figures 2, 3, and 4. At least one air single preheating regenerative burner unit combination 17 is installed on the top of the forehearth 1. The flue gas outlet 18 and the air inlet 19 of the burner are respectively communicated with the air supply pipeline, and the gas inlet 20 of the burner is communicated with the natural gas delivery pipeline. As shown in Figure 2, the air single preheating regenerative burner consists of two sets of regenerators 33 with the same structure, a four-way reversing valve 34, blower 35, and induced draft fan 36 connected by pipelines. There are regenerators 37 distributed. When the burner A is working, the high-temperature exhaust gas after heating the workpiece is discharged through the burner B, and the heat is quickly transferred to the regenerator by radiation and convection. After the flue gas releases heat, the temperature drops to 200°C Below, it is discharged through the four-way valve. After a certain period of time, the four-way reversing valve changes direction, so that the combustion air flows through the regenerator B, and the regenerator quickly transfers heat to the air, the air is preheated to above 800 °C, and the combustion process is completed through the burner B. At the same time, the burner A and the heat storage body A are converted into smoke exhaust and heat storage devices. Through such a reciprocating and alternating operation mode, the limit recovery of flue gas and the preheating of combustion-supporting air can be realized. The heat storage body in the air single preheating regenerative burner unit combination is a honeycomb body made of high aluminum material with compact structure, high compressive strength, high temperature resistance and good impact performance. The new honeycomb heat storage body The temperature difference between the exhaust gas temperature and the preheated air temperature can be reduced to 50-150°C.

As shown in Figure 1, a tubular heat exchanger 21 is installed on the rear furnace body 12 and above the feeding port 13, and the hot air outlets on both sides of the tubular heat exchanger pass through the combustion-supporting secondary air pipe I22 and the rear furnace respectively. The melting zone of the body is connected, and one of the hot air outlets is connected with the air supply pipe through the combustion-supporting secondary air pipe II23. The position of the combustion-supporting secondary air is selected at the position where the temperature of the furnace gas is 700-800°C. Two rows of air outlets can be set with a row spacing of 100-120mm. Each row is equipped with 4-8 air outlets. The diameter of the air outlets is 10-15mm. The air volume and air pressure are not suitable. Too big, determine when adjusting.

As shown in Figure 5, the side wall of the annular fire channel 16 is provided with an air delivery pipe 24 with one end connected to the annular fire channel and the other end connected to the combustion secondary air pipe I22. The air source of the system comes from a steel pipe heat exchanger at 100°C to For preheated air at 150°C, there is a pulverized coal storage funnel 25 connected to it on the air conveying pipe, and a control valve 39 is provided below, and a screw conveyor 26 driven by a power mechanism is installed in the pulverized coal storage funnel, and the pulverized coal storage funnel is above the One side is provided with the pressure balance pipe 27 that is connected with air delivery pipe. An injector 28 and an annular pipe 29 are arranged at the communication place between the annular fire channel 16 and the air delivery pipe 24 . The combustion-supporting air and pulverized coal preheated to 100-150°C in the tubular heat exchanger are sent to the position of the 1/2 H ring of the burner. The diameter of the tuyere is 32-40mm. The air source is shared with the air source of the combustion system, the pulverized coal should be dry, the moisture should be less than 1%, the particle size should be 100-150 mesh, the fixed carbon content should be high, and the S and ash content should be small. , the pulverized coal supply is controlled at 8-10kg/t molten iron, and the air supply volume is 10-11m/kg pulverized coal. Since pulverized coal contains a certain amount of oxygen, H is in an atomic state at a high temperature of 1450°C in the annular flue. It can burn itself and can also promote the combustion of CO. The reaction formula is: CH4+O2==CO2+2H2O CO2+C==2CO.

As shown in Figure 6, a siphon-type slag separation chamber 32 is provided in front of the crater, and curved retaining walls 31 are arranged alternately on both sides of the bridge deck 6 . Firstly, the slag from the rear furnace is removed, and at the same time, a shallow molten pool with a large surface area is opened at the bottom of the bridge. The ports are connected to form two slag separating mechanisms.

The melting furnace is a series of products with a melting rate of 2t to 10t/h. The specific structure of the forehearth can be designed as a horizontal or vertical structure according to specific conditions.

Claims (7)

1. natural gas heat accumulating type cupola furnace, comprise forehearth (1) and back stove (2), be communicated with by burner (3) between forehearth and the back stove, forehearth comprises combustion chamber (4), be opened in the molten bath (5) and the gap bridge between molten bath and burner (6) of bottom, combustion chamber, the both sides, molten bath are respectively equipped with slag-drip opening (7), offer shallow pool (8) on the gap bridge bridge floor, place, arch angle, gap bridge both sides is provided with trough (9) respectively, trough is communicated with the slag-drip opening of both sides, forehearth molten bath, and the combustion chamber is connected with natural-gas transfer pipeline (10) and the air supply duct (11) that communicates with it respectively; Back stove comprises body of heater (12), upper of furnace body is provided with charge door (13), the body of heater top is provided with fume emission mouth (14), bottom of furnace body is provided with convex furnace bottom (15), form annular quirk (16) between convex furnace bottom and the inboard wall of furnace body, the annular quirk is communicated with burner, it is characterized in that forehearth (1) top is equipped with an air single-preheating heat-accumulating burner unit combination (17) at least, the exhanst gas outlet of burner (18), air intlet (19) are communicated with air supply duct respectively, and the fuel gas inlet of burner (20) is communicated with natural-gas transfer pipeline.

2. natural gas heat accumulating type according to claim 1 cupola furnace, it is characterized in that back furnace body (12) upward and above being positioned at charge door (13) is equipped with pipe heat exchanger (21), the hot-air mouth of pipe heat exchanger both sides respectively through combustion-supporting secondary air channel I (22) with after the fusion zone of furnace body be communicated with, one of them hot-air mouth is communicated with air supply duct through combustion-supporting secondary air channel II (23).

3. natural gas heat accumulating type according to claim 1 and 2 cupola furnace, it is characterized in that annular quirk (16) sidewall is provided with the air delivery pipe (24) that an end and annular quirk perforation, the other end are communicated with combustion-supporting secondary air channel I (22), air delivery pipe is provided with the coal dust storage hopper (25) that is communicated with it, the auger conveyor (26) that is driven by actuating unit is installed in the coal dust storage hopper, and coal dust storage hopper top one side is provided with the pressure-equalizing pipe (27) that is connected with air delivery pipe.

4. natural gas heat accumulating type according to claim 3 cupola furnace is characterized in that annular quirk (16) is provided with injector (28) and ring pipe (29) with air delivery pipe (24) place of connection.

5. natural gas heat accumulating type according to claim 1 and 2 cupola furnace is characterized in that the fume emission mouth (14) at furnace body (12) top, back is connected with bag-type dust collector (30).

6. natural gas heat accumulating type according to claim 1 and 2 cupola furnace is characterized in that offering before the burner branch grit chamber (32) of hydrocone type.

7. natural gas heat accumulating type according to claim 1 and 2 cupola furnace, the staggered curve barricade (31) that is provided with in (6) the bridge floor both sides that it is characterized in that passing a bridge.

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