A method for oxygen-enriched combustion with reduced lime double-d kiln coke oven gas blending amount

Abstract

The present application relates to the technical field of metallurgical production, in particular to a method for reducing the mixing amount of coke oven gas in lime double-D kiln by oxygen-enriched combustion, specifically, oxygen injection guns and oxygen-enriched valve groups are installed in the air pipeline of the lime double-D kiln to control the oxygen flow, the lime double-D kiln is started, mixed gas containing coke oven gas and converter gas is introduced, the oxygen-enriched valve groups are then started, the oxygen enrichment degree is set from 1% and gradually increased, and the highest oxygen enrichment degree does not exceed 9%, the air-fuel ratio and the excess air coefficient are simultaneously reduced, and the mixed gas flow is reduced. By the method of oxygen-enriched combustion, the oxygen content in the calcination combustion-supporting air is increased, the combustion efficiency is improved, the combustion temperature is optimized, the air demand and the combustion product generation amount are reduced, the heat taken away by the flue gas is reduced, thereby the heat loss of exhaust gas can be reduced, the theoretical combustion temperature and the furnace gas radiation capacity can be improved, and the energy consumption can be greatly reduced.

Description

An oxygen-enriched combustion method for reducing the amount of coke oven gas blended in a lime double-D kiln Technical Field

[0001] This invention relates to the field of metallurgical production technology, and in particular to an oxygen-enriched combustion method for reducing the amount of coke oven gas blended in a lime double-D kiln. Background Technology

[0002] The double-D vertical kiln for lime is a parallel-flow regenerative vertical kiln. Its principle is that the heat generated by combustion in one chamber is carried by airflow through the connecting channel into another chamber to preheat the stone. It mainly uses mixed gas, which is a mixture of coke oven gas and converter gas, as fuel to calcine lime.

[0003] In the production process of lime double-D kiln, how to reduce the amount of combustion products generated and reduce the amount of coal gas blending while ensuring the quality of lime production has become an urgent problem to be solved. To this end, the present invention provides an oxygen-enriched combustion method to reduce the amount of coke oven gas blending in lime double-D kiln, so as to realize the upgrading and transformation of lime double-D kiln production process. Summary of the Invention

[0004] This invention addresses the aforementioned technical problems and overcomes the shortcomings of existing technologies by providing an oxygen-enriched combustion method for reducing the amount of coke oven gas blended in a double-D lime kiln. By using oxygen-enriched combustion, the oxygen content in the roasting combustion air is increased, combustion efficiency is improved, combustion temperature is optimized, air demand and combustion product generation are reduced, and the heat carried away by the flue gas is reduced. This reduces exhaust heat loss, increases the theoretical combustion temperature and furnace gas radiation capacity, and can significantly reduce energy consumption.

[0005] The oxygen-enriched combustion method for reducing the amount of coke oven gas blended in lime double-D kilns provided in this solution specifically includes the following steps:

[0006] S1. Install oxygen spray guns and oxygen-enriching valve groups in the air pipeline of the double-D lime kiln to control the oxygen flow rate;

[0007] S2. Start the lime double-D kiln production and introduce a mixture of coke oven gas and converter gas;

[0008] S3. Start the oxygen-enriched valve group, adjust the oxygen enrichment setting from 1%, gradually increase the oxygen ratio, and ensure that the oxygen enrichment does not exceed 9% at most. Simultaneously reduce the air-fuel ratio and excess air coefficient, and reduce the mixed gas flow rate.

[0009] The technical solution further defined in this invention is:

[0010] Furthermore, the oxygen enrichment setting starts from 1%. For every 1% increase in oxygen enrichment, the air-fuel ratio of the lime kiln decreases by 5% and the mixed gas flow rate decreases by 3%. The air-fuel ratio is controlled within the range of 1.8 to 2.2, the excess air coefficient is controlled within the range of 1.05 to 1.2, and the fluctuation range of the actual feedback value is controlled within ±10% of the set value.

[0011] Furthermore, in step S3, the quality of the lime is monitored. If the lime is underburned or overburned by ≥20%, the flow rate of the mixed gas is increased. If the lime is underburned or overburned by ≤20%, the oxygen enrichment can be increased further, and the flow rate of the mixed gas can be reduced until 10-15%.

[0012] Furthermore, after reducing the mixed gas flow rate to 10-15%, wait for the furnace temperature to stabilize, monitor the lime quality under this condition, and continue to increase the oxygen enrichment. For every 1% increase in oxygen enrichment, the air-fuel ratio of the lime kiln is reduced by 5% simultaneously, and the coke oven gas blending flow rate is reduced by 5% simultaneously, until the coke oven gas blending flow rate drops below 9%. Record the air-fuel ratio and excess air coefficient every 4 hours.

[0013] Furthermore, in the process of increasing oxygen enrichment and reducing coke oven gas blending flow rate, if the lime is underburned or overburned by ≥20%, the mixed gas flow rate is increased; if the lime is underburned or overburned by ≤20%, the oxygen enrichment is increased and the coke oven gas blending flow rate is reduced until the coke oven gas flow rate is 0.

[0014] Furthermore, in step S2, the proportion of coke oven gas in the mixed gas is 41%.

[0015] The beneficial effects of this invention are:

[0016] (1) The oxygen-enriched combustion method provided by the present invention maintains the original process parameters of the lime kiln unchanged and hardly makes any changes or impacts on the furnace itself. It only increases the oxygen content in the calcination combustion air by installing oxygen spray guns and oxygen-enriched valve groups in the original lime kiln air pipeline, thereby improving combustion efficiency, optimizing combustion temperature, reducing air demand and combustion product generation, and reducing the heat carried away by flue gas. This can reduce exhaust heat loss, increase theoretical combustion temperature and furnace gas radiation capacity, significantly reduce energy consumption, achieve energy saving, and appropriately increase the yield.

[0017] (2) The present invention reduces the calorific value of mixed gas by using oxygen-enriched combustion, reduces the blending ratio of coke oven gas in mixed gas, improves lime quality, reduces gas consumption, especially saves the consumption of high-calorific-value coke oven gas, and replaces some high-calorific-value fuels with low-calorific-value fuels.

[0018] (3) The present invention significantly reduces the amount of combustion products generated by oxygen-enriched combustion, thereby reducing the heat carried away by the flue gas, thus reducing exhaust heat loss, optimizing combustion temperature, appropriately increasing the yield, and reducing fuel consumption. Attached Figure Description

[0019] Figure 1 is a flowchart of the oxygen-enriched combustion method for reducing the amount of coke oven gas blended in a double-D lime kiln according to the present invention.

[0020] Figure 2 is a schematic diagram of the oxygen-enriched combustion interlock valve connection in an embodiment of the present invention. Detailed Implementation

[0021] This embodiment takes four lime kilns as an example. The oxygen main pipe needs to consider the total oxygen demand of the four lime kilns, based on 2000 Nm³. 3 The design involves manually and remotely adjusting the blending of coke oven gas into the converter gas based on its calorific value, resulting in a blended calorific value of 1900-2100 kcal / Nm³. 3 To ensure lime quality, the main modification goals are to improve lime quality and reduce gas consumption, especially saving on the consumption of high-calorific-value coke oven gas. This embodiment maintains the original process parameters of the lime kiln unchanged, with almost no alteration or impact on the kiln itself. Energy consumption can be significantly reduced by installing oxygen lances and oxygen-enriched valve groups in the original lime kiln air pipeline, achieving energy conservation. Simultaneously, the use of oxygen enrichment technology reduces the calorific value of the mixed gas and decreases the proportion of coke oven gas blended in the mixed gas. Each furnace chamber of the double-chamber lime kiln is equipped with 24 gas lances, totaling 48 lances. Both furnace chambers have DN700 air inlets with shut-off valves at the top. The air flow direction is switched by the interlocking opening and closing of the two shut-off valves (switching occurs approximately every 12 minutes).

[0022] The scope of implementation involves upgrading the lime kiln to oxygen-enriched combustion on-site, using a new oxygen distributor combined with an oxygen-enriched valve assembly to automatically control the oxygen flow. The main equipment is as follows:

[0023] 1. Oxygen-enriched valve assembly: Oxygen-HLL (500Nm) 3 / h), dedicated oxygen lance, connecting pipeline

[0024] 2. Construction Content

[0025] 1) Lay oxygen pipelines to the designated TOP point and install shut-off valves. Seal the ends with flanges and blind flanges. Pipeline construction shall be carried out in accordance with relevant specifications.

[0026] 2) Conduct pressure testing and leak testing on the laid oxygen pipelines according to specifications. All flange connections of the pipelines (including the valve stations and other equipment provided by the client) shall be treated with anti-static measures.

[0027] 3) Installation of oxygen-enriched valve assembly: The valve assembly is installed by skid mounting and fixed in the designated position, with necessary guardrails and other protective devices. After purging, it is connected to the oxygen pipeline inlet.

[0028] 4) Drill holes in the original air duct and install and fix the oxygen spray gun. The installation angle must be reversed according to regulations.

[0029] 5) Connect to the fan flow signal and activate the safety interlock procedure.

[0030] Debugging steps and requirements:

[0031] 1. Slowly open the oxygen valve assembly and all manual valves in the pipeline;

[0032] 2. Select "Manual" mode for control and click the "Start Oxygen-Enriched Valve Assembly" button on the operation panel;

[0033] 3. Observe the oxygen pressure after passing through the oxygen pressure reducing valve; the outlet pressure after pressure reduction is 0.1-0.4 MPa.

[0034] 4. When adjusting the oxygen enrichment setting, start with 1% and gradually increase the oxygen ratio, with the maximum oxygen enrichment not exceeding 9%. The air-fuel ratio and excess air coefficient of the lime kiln should be reduced by 5% from the original setting. As the oxygen enrichment gradually increases, the air-fuel ratio and excess air coefficient should be gradually reduced, and the gas flow rate should be reduced.

[0035] 5. Maintain the original production capacity of the lime kiln and start the double-D lime kiln normally. Under stable production conditions, click "Start Lime Kiln Oxygen Enrichment" on the main interface. The valve group will automatically adjust the hourly oxygen flow rate according to the lime kiln's air volume and oxygen enrichment setting.

[0036] 6. The specific steps are as follows:

[0037] (1) Adjustment plan to reduce mixed gas consumption (without reducing coke oven gas, mainly implemented in the first stage)

[0038] 1) Record the main parameters such as furnace pressure, connection channel temperature, flue gas temperature, and product quality under the original production mode of the double-D lime kiln;

[0039] 2) The oxygen enrichment setting starts at 1%. For every 1% increase in oxygen enrichment, the air-fuel ratio of the lime kiln decreases by 5%, and the mixed gas flow rate decreases by 3%. Based on the cut-off temperature of the double-D kiln channel, if the connecting channel temperature rises rapidly, the decrease in mixed gas flow rate should be appropriately increased. If the cut-off temperature is reached, the original cut-off temperature operating guidelines should be followed. If the connecting channel temperature shows a stable downward trend, the gas flow rate into the kiln should be appropriately increased. Once the furnace temperature stabilizes, the lime quality should be monitored under this condition.

[0040] 3) Repeat the above steps until the mixed gas flow rate decreases by about 10-15%; monitor the quality of the lime. If the lime is underburned or overburned by ≥20%, gradually increase the mixed gas flow rate; if the lime is underburned or overburned by ≤20%, continue to increase the oxygen enrichment and decrease the mixed gas flow rate according to step 2) until the appropriate flow rate is reached.

[0041] 4) Maintain this state for 1-2 days and record all parameters of the lime double-D kiln under this state. Then shut down the oxygen-enriched lime kiln and restore the original production mode by recording the data in step 1).

[0042] (2) Reduce coke oven gas commissioning plan (reduce coke oven gas, all four kilns operate simultaneously):

[0043] 1) Record the main parameters such as furnace pressure, connection channel temperature, flue gas temperature, and product quality under the original production mode of the double-D lime kiln;

[0044] 2) The oxygen enrichment setting starts at 1%. For every 1% increase in oxygen enrichment, the air-fuel ratio of the lime kiln decreases by 5%, and the coke oven gas mixing flow rate decreases by 5%. Using the cut-off temperature of the double-D kiln channel as a benchmark, if the connecting channel temperature rises rapidly, the decrease in the coke oven gas mixing flow rate should be appropriately increased. If the cut-off temperature is reached, the original cut-off temperature operating guidelines should be followed. If the connecting channel temperature shows a stable downward trend, the inlet gas flow rate should be appropriately increased. Once the furnace temperature stabilizes, monitor the lime quality under this condition.

[0045] 3) Repeat the above steps, gradually increasing the oxygen enrichment until the coke oven gas content drops below 9%. Monitor the lime quality; if the lime is underburned or overburned by ≥20%, the kiln gas flow rate needs to be adjusted accordingly; if the lime is underburned or overburned by ≤20%, continue with step 2) until the coke oven gas is completely eliminated.

[0046] 4) Maintain this state of continuous operation and record the parameters of the double-D lime kiln under this state.

[0047] See Table 1 for a comparison of energy consumption before and after the renovation of the four lime kilns (D kilns).

[0048] Table 1

[0049]

[0050] In this embodiment, under the premise of ensuring lime kiln output and product quality, after oxygen enrichment modification, the consumption of coke oven gas can be further reduced by continuing to increase the flow rate of converter gas. At the same time, the oxygen consumption also needs to be increased to a certain extent. The specific comparative analysis is shown in Table 2 below (total of four lime kilns).

[0051] Table 2

[0052]

[0053] Oxygen-enriched combustion significantly reduces the amount of combustion products generated, thereby reducing the heat carried away by the flue gas, which in turn reduces exhaust heat loss, optimizes combustion temperature, appropriately increases product yield, and reduces fuel consumption.

[0054] The benefit analysis is based on a single 300t / d double-chamber lime kiln and the following energy prices:

[0055] The combined price of mixed coal gas is 59 yuan / GJ (converter gas 50.64 yuan / GJ, coke oven gas 63.08 yuan / GJ); oxygen price: 0.44 yuan / Nm³. 3 The electricity price is 0.6 yuan / kWh.

[0056] The economic benefits before and after the oxygen-enrichment transformation are compared and analyzed in Table 3 below.

[0057] Table 3 Comparison of Benefits Before and After Oxygen-Enrichment Modification

[0058]

[0059] This embodiment significantly improves the combustion quality, increases the combustion temperature, shortens the calcination time, and enhances the flexibility of fuel use by optimizing the oxygen-enriched combustion process in lime kilns. The oxygen-enriched combustion in the lime kiln is stable and orderly, with the following advantages:

[0060] (1) Reduce air demand and combustion product generation

[0061] As the oxygen content in the combustion air increases, the air demand and the amount of combustion products generated decrease.

[0062] (2) Increase the theoretical combustion temperature

[0063] As the oxygen content in the air increases, the amount of combustion products decreases significantly, and the theoretical combustion temperature will inevitably rise.

[0064] (3) Improve the furnace gas radiation capacity

[0065] After combustion, the content of CO2 and H2O in the flue gas increases, especially the content of CO2. The main radioactive gases in the flue gas are CO2 and H2O.

[0066] (4) Reduce energy consumption by replacing some high-calorific-value fuels with low-calorific-value fuels.

[0067] Based on the on-site airflow and oxygen supply conditions, oxygen enrichment is adopted in the main pipe. The oxygen enrichment level of the valve group is controlled at 3-8%, and the peak oxygen flow rate required for a single lime kiln is controlled at 500 Nm³. 3The oxygen-enriched system design, based on actual site conditions, involves extending an oxygen pipeline from the main oxygen pipe connected to the lime kiln to the combustion air pipeline. After pressure and flow regulation, the oxygen enters the main air supply pipe of the combustion air blower. A pressure-reducing valve assembly and a flow-regulating valve assembly are installed between the main oxygen pipe and the combustion air pipeline, along with relevant instruments. Related control screens are added to the existing control system, or a separate control cabinet is installed, to achieve system monitoring and operation functions.

[0068] The first step is to gradually increase the oxygen enrichment while reducing the flow rate of mixed gas, under the premise of ensuring the production process, product output and quality, so as to achieve the optimal ratio of mixed gas, oxygen and combustion air under stable production conditions.

[0069] The second step, also under the premise of ensuring production process and product output and quality, is to first maintain stable gas flow, gradually increase oxygen enrichment, and at the same time reduce the blending ratio of coke oven gas in the mixed gas, adjusting it to the minimum coke oven gas blending ratio under stable production conditions.

[0070] In addition to the embodiments described above, the present invention may have other implementations. All technical solutions formed by equivalent substitution or equivalent transformation fall within the protection scope claimed by the present invention.

Claims

1. A method for oxygen-enriched combustion to reduce the amount of coke oven gas blended in a lime double-D kiln, characterized in that, Includes the following steps: S1. Install oxygen spray guns and oxygen-enriching valve groups in the air pipeline of the double-D lime kiln to control the oxygen flow rate; S2. Start production in the double-D lime kiln, introducing a mixed gas containing coke oven gas and converter gas; S3. Start the oxygen-enriched valve group, adjusting the oxygen enrichment setting from 1%, gradually increasing the oxygen ratio, with the oxygen enrichment not exceeding 9%, simultaneously reducing the air-fuel ratio and excess air coefficient, and reducing the mixed gas flow rate; starting from 1%, for every 1% increase in oxygen enrichment, the air-fuel ratio of the lime kiln decreases by 5%, and the mixed gas flow rate decreases by 3%; in step S3, monitor the lime quality. If the lime is underburned or overburned by ≥20%, increase the mixed gas flow rate; if the lime is underburned or overburned by ≤20%, continue to increase the oxygen enrichment and decrease the mixed gas flow rate until it reaches 10-15%; after reducing the mixed gas flow rate to 10-15%, wait for the furnace temperature to stabilize, monitor the lime quality under this state, and continue to increase the oxygen enrichment. For every 1% increase in oxygen enrichment, the air-fuel ratio of the lime kiln decreases by 5%, and the coke oven gas blending flow rate decreases by 5%, until the coke oven gas blending flow rate drops below 9%.

2. The oxygen-enriched combustion method according to claim 1, characterized in that, In the process of increasing oxygen enrichment and reducing coke oven gas blending flow rate, if the lime is overburned by ≥20%, the mixed gas flow rate is increased; if the lime is overburned by ≤20%, the oxygen enrichment is increased and the coke oven gas blending flow rate is reduced until the coke oven gas flow rate reaches 0.

3. The oxygen-enriched combustion method according to claim 1, characterized in that, In step S2, the proportion of coke oven gas in the mixed gas is 41%.

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