A wet desulfurization method for demineralized water

Abstract

The present invention discloses a wet desulfurization method for demineralized water. First, the waste heat power generation system is used to collect river water, and the river water is subjected to precipitation, filtration, primary demineralized water and secondary demineralized water to obtain secondary demineralized water; ammonia water is added to the secondary demineralized water to control the pH value; the secondary demineralized water is led out from the feed water pump to the boiler section, and after being led out, it is divided into two paths, one is path A and the other is path B; the demineralized water is atomized and sprayed into the reaction zone through a special spray gun to capture SO in the flue gas 2 . The present invention reduces the enrichment and circulation of sulfur in the system, stabilizes sulfur emissions, reduces sulfur emissions, reduces production costs, reduces the impact on the kiln system operating conditions, and can achieve ultra-low cost desulfurization.

Description

Technical Field

[0001] The present invention relates to the technical field of desulfurization for cement clinker production, and particularly to a wet desulfurization method using demineralized water. Background Art

[0002] Currently, in cement clinker production, the raw fuels and materials generally contain high sulfur, resulting in a large amount of sulfur dioxide emissions. Commonly, a composite desulfurization technology is used for desulfurization, which combines the fixed sulfur in the kiln using desulfurization powder and increasing the desulfurization efficiency at the backend with water agent through a composite desulfurization route. The desulfurization powder is added from the air chute at the front end of the elevator entering the kiln and mixed with the raw meal into the kiln; the desulfurization water agent is sprayed at the rising pipe of the second to first-stage preheater. From the principle perspective, this composite desulfurization mainly oxidizes SO 2 to SO 3 , removes a part with calcium-based, and then removes it with amino-based. This desulfurization method has the following deficiencies:

[0003] 1. High operating cost: The unit price of desulfurization powder ≥ 850 yuan / ton, and the unit price of desulfurization water agent ≥ 540 yuan / ton. If the SO 2 body concentration is 400 mg / Nm 3 , the raw meal mill itself absorbs about 50% during operation. Reducing from 200 mg / Nm 3 to 50 mg / Nm 3 , generally 0.5 - 0.8 t / h of powder or 1.2 - 1.5 m3 / h of water agent is required, resulting in high operating costs.

[0004] 2. Some of the generated products, sulfate, have poor thermal stability, causing secondary decomposition, cyclic enrichment, poor continuous stability, and easy corrosion of equipment.

[0005] 3. Adding desulfurization powder causes fluctuations in the raw meal composition and affects the burnability.

[0006] 4. The spraying point of the desulfurization water agent is at the rising pipe of the second to first-stage preheater, which cools the system indirectly and increases energy consumption. Summary of the Invention

[0007] The purpose of the present invention is to provide a wet desulfurization method using demineralized water. According to the wet desulfurization method using demineralized water of the present invention, it can be widely applied to the cement clinker production process with a waste heat power generation system. The wet desulfurization technology using demineralized water can assist in absorbing some sulfur emissions from the absorption system, reduce the sulfur emission concentration, and assist in achieving the standard of sulfur emissions, saving production costs. The technical solution adopted by the present invention is as follows:

[0008] According to one aspect of the present invention, a wet desulfurization method using demineralized water is provided, and the method includes the following steps:

[0009] (1) Preparation of demineralized water: Collect river water, place the river water in the raw water integrated water tank for precipitation to obtain standing water, filter the standing water with the filter in the water treatment workshop to obtain filtered liquid, perform primary desalination on the filtered liquid using a reverse osmosis membrane to obtain primary demineralized water, remove calcium ions and magnesium ions in the mixed bed, and perform secondary desalination in the demineralized water tank to obtain secondary demineralized water;

[0010] (2) Add 0.02% ammonia water to the secondary demineralized water to control the pH value at 8.3 ± 0.2, and guide the secondary demineralized water mixed with ammonia water to the boiler through a feed water pump;

[0011] (3) Draw out the secondary demineralized water from the section between the feed water pump and the boiler. After drawing out, it is divided into two paths. One path is path A, and path A is led to the inlet pipeline of the humidification tower and the inlet pipeline of the hot air pipe of the vertical mill; the other path is path B, and path B is led to the inlet pipeline of the waste gas chimney;

[0012] (4) The one led to the inlet pipeline of the humidification tower is A1, and the one led to the inlet pipeline of the hot air pipe of the vertical mill is A2. When the vertical mill stops, A1 is opened for use; when the vertical mill is running, A2 is opened for use; Install atomizing spray guns on the pipeline, and capture SO on its cross-section 2 ;

[0013] (5) Path B is led to the inlet pipeline of the waste gas chimney, and a shower-type atomizing nozzle is used. An atomizing bed is formed by combining the three surfaces above, on the left and on the right of the pipeline to capture SO 2 , when the emission of SO 2 is high, the atomizing nozzle is in the normally open state to capture SO 2 .

[0014] Preferably, the raw water integrated water tank in step (1) is a multi-media filter, and a flocculant and a coagulant aid are added to the multi-media filter to perform precipitation treatment on the river water.

[0015] Preferably, the filter in the water treatment workshop in step (1) is an activated carbon filter, and a scale inhibitor is added to the activated carbon filter.

[0016] Preferably, the pressure of the feed water pump in step (2) is 1.5 Mpa.

[0017] Preferably, the atomizing spray gun in step (4) is a linear atomizing spray gun, and 3 are arranged at intervals in the cross-section of the pipeline, arranged in a fan shape.

[0018] Preferably, a return water system is provided at the bottom of the inlet pipeline of the waste gas chimney in step (5). The return water system includes a drainage tank. One end of the drainage tank is welded to the inlet pipeline of the waste gas chimney, and the other end of the drainage tank is connected to the collection tank in the sewage treatment workshop.

[0019] The above technical solution adopted by the present invention has the following remarkable effects:

[0020] (1) The present invention uses the alkaline demineralized water self-made by the waste heat power generation system for desulfurization, and arranges the desulfurization points at the inlet pipelines of the humidifying tower, the hot air pipeline of the vertical mill, and the inlet pipeline of the waste gas chimney that have no influence on the firing system. The demineralized water is atomized and sprayed into the reaction zone through a special spray gun to capture SO 2 in the flue gas, with low operating costs, convenient adjustment, low implementation difficulty, and great significance for popularization.

[0021] (2) The present invention reduces the enrichment and circulation of sulfur in the system, stabilizes sulfur emissions, reduces sulfur emissions, reduces production costs, reduces the impact on the operating conditions of the kiln system, and can achieve ultra-low-cost desulfurization. Specific Embodiments

[0022] To make the purpose, technical solutions and advantages of the present invention clearer and more understandable, the following preferred embodiments are cited for further detailed description of the present invention. However, it should be noted that many details listed in the specification are only for enabling the reader to have a thorough understanding of one or more aspects of the present invention, and these aspects of the present invention can be implemented even without these specific details.

[0023] According to a method for wet desulfurization with demineralized water of the present invention, the method includes the following steps:

[0024] Inspection before starting the system:

[0025] Open the connection valve from the pump house (water treatment workshop) to the raw water tank to fill the raw water tank with water (raw water turbidity < 1 NTU).

[0026] Check that the liquid levels of the flocculant solution tank and the scale inhibitor solution tank are not lower than 1 / 2.

[0027] Check that all the equipment to be put into operation is in good standby state.

[0028] Commissioning operation:

[0029] Open the outlet valve of the raw water tank, check that the inlet valve of the raw water pump is open, add flocculant in the multi-media filter (adjust the dosing according to the dosing required by the commissioning results, with the initial set value of 5 mg / L); check that the air valve of the multi-media filter is open, start the raw water pump, open the outlet valve of the raw water pump, open the inlet valve of the multi-media, and after the air valve overflows with water, open the lower drain (positive flushing) valve of the multi-media filter, close the air valve of the multi-media filter, and conduct positive flushing for 2 - 3 minutes (measure the turbidity < 0.5 NTU, qualified).

[0030] Check that the air valve of the activated carbon filter is open. Open the inlet valve of the activated carbon filter, open the outlet valve of the multi-media filter, and close the bottom drain (pre-flushing) valve of the multi-media filter. After the air valve of the activated carbon filter overflows with water, open the bottom drain (pre-flushing) valve of the activated carbon filter and close the air valve. Take a sample to detect the outlet water (turbidity < 0.5 NTU, SDI < 4, pH: 4 - 9). After the water quality indicators are qualified, prepare to feed water into the R / O. The filter has strong adsorption and dirt interception capabilities during filtration, removing the residual amounts of impurities such as colloidal microorganisms and some particulate suspended solids.

[0031] Open the inlet valve of the security filter, fully open the R / O inlet water electric valve, and open the R / O concentrated water electromagnetic (discharge) valve. Open the outlet valve of the activated carbon filter, adjust the bottom drain valve of the activated carbon filter, and keep the outlet water pressure of the activated carbon filter between 0.2 - 0.3 Mpa. Conduct a low-pressure flushing of the R / O device for 5 minutes.

[0032] Start the scale inhibitor dosing pump (maintain the dosing amount at 3 PPM).

[0033] When the R / O inlet water electric valve is closed and then reopened to 1 / 3, start the R / O high-pressure pump and close the normal drain valve of the activated carbon filter.

[0034] Adjust the inlet control valve and the concentrated water regulating valve to make the inlet water pressure reach above 1.0 Mpa, and the ratio of the water production rate to the concentrated water discharge rate is 3:1 (15 t / h: 5 t / h). Confirm that the operating parameters of the RO membrane module are all normal (that is, the pressure difference between the inlet water pressure, the inter-stage pressure, and the concentrated water pressure is maintained within 0.25 Mpa). Detect that the R / O outlet water conductivity < 10 us / cm. Close the R / O concentrated water solenoid valve, open the unqualified water discharge valve and then slowly close it to keep the R / O outlet water flow at 15 t / h, and send water to the intermediate water tank. Reverse osmosis technology can remove more than 90% of the ions in water, such as organic matter and silicon in water.

[0035] When the water level in the intermediate water tank is higher than 1 / 2, open the inlet valve of the intermediate water pump, check that the air valve of the mixed bed is open, start the intermediate water pump, open the outlet valve of the intermediate water pump, open the inlet valve of the mixed bed. After the air valve of the mixed bed overflows with water, open the normal flushing valve of the mixed bed and close the air valve. After the mixed bed is normally flushed until the outlet water is qualified (conductivity ≤ 1 µs / cm), open the outlet valve of the mixed bed and send water to the demineralized water tank.

[0036] The demineralized water tank undergoes secondary desalination to obtain secondary demineralized water. The main indicators of the secondary demineralized water (parameters: conductivity ≤ 1 μS / cm, silica ≤ 10 μg / L, pH ≤ 6). Add 0.02% ammonia water to the secondary demineralized water to control the pH value at 8.1 - 8.5, and conduct the secondary demineralized water mixed with ammonia water to the boiler through the feed water pump. The qualified secondary demineralized water enters the vacuum deaerator, and the boiler feed water is treated by the vacuum deaeration method, creating a redox atmosphere and forming a protective film even at low temperatures, thus preventing the corrosion of equipment and pipelines. At the same time, the feed water pH only needs to be controlled between 8.7 and 8.9, extending the boiler pickling cycle and effectively reducing the operating cost of the unit. The pressure of the waste heat boiler feed water pump reaches 1.5 Mpa, and no booster is required.

[0037] Secondary demineralized water is led out from the section between the feed water pump and the boiler. After being led out, it is divided into two paths. One path is path A, and path A is led to the inlet pipeline of the humidification tower and the inlet pipeline of the hot air pipe of the vertical mill; the other path is path B, and path B is led to the inlet pipeline of the waste gas chimney.

[0038] The one led to the inlet pipeline of the humidification tower is A1, and the one led to the inlet pipeline of the hot air pipe of the vertical mill is A2. When the vertical mill stops running, A1 is opened for use; when the vertical mill is running, A2 is opened for use; atomizing spray guns are set on the pipeline to capture SO on its cross-section 2 . Among them, the atomizing spray gun is a linear atomizing spray gun, and 3 are arranged at intervals in the pipeline cross-section, arranged in a fan shape.

[0039] Path B is led to the inlet pipeline of the waste gas chimney, and a shower-type atomizing nozzle is used to form an atomizing bed on the upper, left, and right three sides above the pipeline to capture SO 2 , when the SO 2 emission is high, the atomizing nozzle is in the normally open state to capture SO 2 . Among them, a water return system is provided at the bottom of the inlet pipeline of the waste gas chimney. The water return system includes a drainage tank. One end of the drainage tank is welded to the inlet pipeline of the waste gas chimney, and the other end of the drainage tank is connected to the collection tank in the sewage treatment workshop.

[0040] Among them, the water treatment process is: river water → raw water tank → raw water pump → multi-media filter (adding flocculant and coagulant aid) → activated carbon filter (adding scale inhibitor) → security filter → high-pressure pump → reverse osmosis system → intermediate water tank → intermediate water pump → mixed ion exchange bed → resin catcher → demineralized water tank → demineralized water pump (adding ammonia) → deaerator feed water.

[0041] Adopting the method of the present invention has the following effects:

[0042] 1. Low cost of self-made demineralized water: Electricity cost per ton of water production + Ammonia water cost per ton of demineralized water = Cost per ton of demineralized water. (4 pumps (22 kW) * 0.5 (yuan / kWh) / 11 (tons / hour)) + 1 * 0.12% * 1050 (yuan / ton) = 2.26 yuan / ton;

[0043] 2. The demineralized water has low hardness (≤3 μmol / L) and weak alkaline pH value of 8.3 ± 0.2, without scaling or corrosion;

[0044] 3. The desulfurization point is arranged at the rear end of the firing system, without affecting calcination;

[0045] 4. The atomization bed and the return water system of the waste gas chimney pipeline are located at the end of the entire production system. The absorbed sulfur will not return to the firing system with the raw meal, reducing sulfur circulation.

[0046] 5. The wet desulfurization technology of demineralized water helps to achieve the standard of sulfur emissions, saves production costs, and can be popularized and used similarly.

[0047] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A wet desulfurization method for demineralized water, which is applied to a cement clinker production system, Characterized in that: The method comprises the following steps: (1) Collect river water, place the river water in an integrated raw water tank for sedimentation to obtain standing water, filter the standing water with a filter in the water treatment workshop to obtain filtrate, perform primary desalination on the filtrate using a reverse osmosis membrane to obtain primary demineralized water, remove calcium ions and magnesium ions in a mixed bed, and perform secondary desalination in a demineralized water tank to obtain secondary demineralized water; (2) Add 0.02% ammonia water to the secondary demineralized water to control the pH value at 8.3 ± 0.2, and guide the secondary demineralized water mixed with ammonia water to the boiler through a feed water pump; (3) Draw out secondary demineralized water in the section from the feed water pump to the boiler. After drawing out, it is divided into two paths. One path is path A, and path A is led to the inlet pipeline of the humidifying tower and the inlet pipeline of the hot air pipe of the vertical mill; the other path is path B, and path B is led to the inlet pipeline of the waste gas chimney; (4)The pipe leading to the inlet of the humidifying tower is A1, and the pipe leading to the inlet of the hot air pipe of the vertical mill is A2. When the vertical mill stops, A1 is opened for use; when the vertical mill is running, A2 is opened for use; atomizing spray guns are installed on the pipes, and SO is captured on its cross-section 2 , and the atomizing spray guns are linear atomizing spray guns, and 3 are arranged at intervals in the cross-section of the pipe, arranged in a fan shape (5) The B path leads to the inlet pipe of the waste gas chimney. A shower - type atomizing nozzle is used, and an atomization bed is formed by combining the upper, left, and right sides of the pipe to capture SO 2 , when the SO 2 emission is high, the atomizing nozzle is in an always - open state to capture SO 2 . A water return system is provided at the bottom of the inlet pipe of the waste gas chimney. The water return system includes a drainage trough. One end of the drainage trough is welded to the inlet pipe of the waste gas chimney, and the other end of the drainage trough is connected to the collection tank in the sewage treatment workshop.

2. A wet desulfurization method for demineralized water according to claim 1, Characterized in that: The integrated raw water tank in step (1) is a multi-media filter, and a flocculant and a coagulant aid are added to the multi-media filter for sedimentation treatment of river water.

3. A wet desulfurization method for demineralized water according to claim 1, Characterized in that: The filter in the water treatment workshop in step (1) is an activated carbon filter, and a scale inhibitor is added to the activated carbon filter.

4. A wet desulfurization method for demineralized water according to claim 1, Characterized in that: The pressure of the feed water pump in step (2) is 1.5 Mpa.