Details

Application of calcium based superfine powder desulfurization (instead of baking soda) in steel, coking and waste incineration industries

After decades of rapid development, environmental issues have attracted more and more attention; President Xi put forward the environmental protection concept of "green water and green mountains are golden mountains" very early. China has also committed to the international goal of reaching the peak of carbon and carbon integration, which fully reflects the responsibility of a major country;


Ultra low emission and pollutant treatment have become the urgent problems to be solved in the steel industry, coking industry and waste incineration industry. In order to achieve the environmental protection standard, many environmental protection treatment technologies have been widely used. The application of many technologies has indeed made the environmental protection situation in all walks of life better overall, with great improvement and progress;


However, we also noticed that the application of some environmental protection technologies has brought more environmental protection problems while solving some environmental protection problems;


1. Incidental problems of sulfide treatment

It is well known that in the production process of iron and steel enterprises, coking enterprises and waste incineration enterprises, the flue gas generated by the combustion of various types of fuel media will contain sulfide, nitrogen oxides, dust and other pollutants;

According to the requirements of national environmental protection policies, various provinces, cities and regions are successively carrying out smoke pollutant treatment;


1.1 Introduction to SDS dry process (sodium bicarbonate) desulfurization

Among them, SDS dry desulfurization is widely used for sulfide treatment:

1.1.1 Process flow

(1) . The flue gas is introduced into the reaction tower, and then enters the pure dry desulfurization system (NaHCO3). By spraying sodium bicarbonate ultrafine particles into the reaction tower, the sodium bicarbonate ultrafine particles decompose into highly active sodium carbonate under the action of high-temperature flue gas, and generate carbon dioxide and water. The highly active sodium carbonate fully contacts with SO2, SO3 and other acidic components in the flue gas of the heating furnace and has chemical reaction to achieve the solidification and removal of SO2, Ensure that the SO2 concentration at the outlet is ≤ 25mg/Nm3 (as required).


Microscopic images before and after baking soda heat activation


(2) The by-products from the desulfurization system enter the subsequent bag type dust removers along with the flue gas. After the bag type interception and capture, the particle concentration in the flue gas at the outlet of the bag type dust remover is ≤ 10mg/Nm3 (as required). In addition, the unreacted sodium carbonate will also adhere to the surface of the filter bag. When the flue gas passes through the filter bag, SO2 in the flue gas will continue to react with sodium carbonate to achieve the secondary removal of SO2 and further improve the desulfurization efficiency.


The dust collected by the bag filter can be collected by the centralized ash bin, and the specific method can be determined according to the actual layout of the site.


1.1.2 Equipment and facilities

1) Basic process

(1) The purchased desulfurizer raw materials (NaHCO3 powder, about 200 meshes) are sent to the NaHCO3 storage bin for storage. The storage bin volume meets the desulfurizer consumption requirements for 5-day full load operation.

(2) Send the NaHCO3 raw materials to the grading grinder, and grind the NaHCO3 to about 700 meshes through grading grinding.

(3) . The ground hydrogen carbonate superfine powder is sent to the reactor through the injection system, and the sodium bicarbonate superfine particles decompose into highly active sodium carbonate under the action of high-temperature flue gas, and generate carbon dioxide and water; The highly active sodium carbonate fully contacts with SO2, SO3 and other acidic components in the flue gas of the heating furnace and chemical reaction takes place to realize the solidification and removal of SO2.


图片 3.png

Pyrolysis principle of baking soda


2) Working principle

Under the action of high-temperature flue gas (more than 140 ℃), NaHCO3 superfine powder rapidly decomposes to generate highly active Na2CO3 particles, carbon dioxide and water. Because the particle size is very small, the carbon dioxide and water generated inside the particle will break the outer surface of the particle, shaping the Na2CO3 particle into a highly active substance with a large number of micropores and specific surface area, which can quickly react with acid substances (SO2, SO3, etc.) in the flue gas.


Main reaction:      2NaHCO3 (s)=Na2CO3 (s)+H2O (g)+CO2 (g)            (1)

                             SO2(g)+Na2CO3(s) = Na2SO3(s)+CO2(g)                  (2) 

Part:                      SO2 (g)+Na2CO3 (s)+O2=Na2SO4 (s)+CO2 (g)        (3)

Side reaction:       SO3 (g)+Na2CO3 (s)=Na2SO4 (s)+CO2 (g)               (4)

                             2HCL(g)+Na2CO3(s) = 2NaCL(s)+CO2(g)                  (5)


3) System composition: the pure dry desulfurization system is mainly composed of the following parts:

(1) Desulfurizer storage system: mainly including NaHCO3 storage bin and supporting auxiliary equipment.

(2) Dry powder grinding and spraying system: the core equipment is a NaHCO3 grinder, which grinds NaHCO3 powder from 200 meshes to about 700 meshes of ultra-fine powder to meet the requirements of the desulfurization system for raw materials; Then, the superfine powder is sprayed into the respective flue reactor through the supporting direct blowing fan.

(3) Desulfurization reactor: ensure sufficient contact reaction time between flue gas and desulfurizer.


1.2 The problems and solutions of SDS dry desulfurization, namely the advantages of calcium based direct injection technology:

Serial NoProblemsSolutionAdvantages of calcium based direct injection technology
1Sodium bicarbonate is used as desulfurizer. With the continuous increase of flue gas desulfurization projects, the supply of sodium bicarbonate is often in short supply, and the price is rising and the operating cost is increasing;Through laboratory experiments, engineering case practices and other ways, our company has introduced the calcium hydroxide superfine powder direct injection technology and calcium based desulfurizer suitable for this technology, which can be used instead of baking soda;It solves the problem that the supply of baking soda exceeds the demand and the cost of baking soda keeps rising, leading to a substantial increase in operating costs;
2When baking soda is used, equipment and facilities such as a grinder are required for grinding, and can only be used after reaching 700 meshes or even 900 meshes (meeting the effect requirements). The one-time investment is high, the operation cost (power consumption) is increased, and the maintenance points are increased;After using this calcium based desulfurizer, it is unnecessary to use mill equipment and facilities, and the superfine powder can be directly transported by compressed air;Reduce one-time investment (no mill and other facilities are required for new projects) and operating costs (no mill power consumption costs);
3The desulfurization product of this method is sodium sulfate. After sampling and testing several projects, the product composition is complex and difficult to handle, and the positioning of sodium sulfate (solid waste or hazardous waste) has not been clearly defined;After using this calcium based desulfurizer, the product is calcium sulfate (containing calcium carbonate and unreacted calcium hydroxide, etc.), which is easier to treat than sodium sulfate, and belongs to the category of by-product or solid waste. Our company can carry out the corresponding recovery work;Thus, the problem that the by-product is difficult to treat or the treatment cost is high is solved;
4When baking soda is used for desulfurization, the reaction temperature of flue gas is generally 180~280 ℃, and the desulfurization efficiency is high. The flue gas temperature of steel, coking, cement and other industries is low, so the flue gas needs to be heated to increase energy consumption;With this calcium based desulfurizer, the range of flue gas desulfurization temperature is wider (35~350 ℃), which is more energy saving than baking soda.Solve the problem of flue gas temperature rise at the desulfurization inlet and reduce the operation cost
5When baking soda is used for desulfurization, its defluorination ability is weak, which is not conducive to the integrated device of flue gas desulfurization, denitrification and dust removal (fluorine corrosion metal filter tubes, composite ceramic tubes, etc. in flue gas)After using this calcium based desulfurizer, the fluorine in the flue gas generates GaF2, while the stability of NaF is higher, so calcium based desulfurizer is easier to defluoride than sodium based desulfurizer.Solve the impact of fluorine in flue gas on the desulfurization, denitrification and dust removal integrated device,
6The moisture in flue gas has little effect on desulfurization efficiency when baking soda is used for desulfurization;After the calcium based desulfurizer is used, the moisture in the flue gas has a greater impact on the desulfurization efficiency. When the moisture is higher, the desulfurization efficiency of the calcium based desulfurizer is higher, reducing the corrosion of the moisture in the flue gas on the flue and equipment.Solve the impact of high moisture content in flue gas on flue and equipment.


· It can be seen from the above that after calcium base is used to replace sodium base, namely calcium base direct injection technology is used:

· It solves the situation that the supply of baking soda exceeds the demand due to the increasing number of desulfurization projects, which will not affect the continuity and stability of enterprise production;

· It solves the problem that the price of baking soda keeps rising and the operating cost of the enterprise keeps increasing;

· The influence of flue gas temperature on desulfurization efficiency is solved;

· The influence of fluorine in flue gas on a desulfurization, denitration and dust removal integrated device is solved;

· The higher the moisture in the flue gas (within a certain range), the higher the desulfurization efficiency;

· Reduce one-time investment and increase of power consumption cost during operation (operation cost is saved by more than 30%);

· Desulfurization products are easy to handle, and our company can recycle them;


2. Application of calcium based desulfurization (instead of baking soda) in iron and steel industry


In the production process of iron and steel enterprises, according to the need of overall energy medium balance, various energy mediums such as blast furnace gas, converter gas, coke oven gas, etc. will be used in various types of furnaces, such as hot blast furnaces, power plant boilers, steel rolling plant heating furnaces, etc. During the production process of furnaces, the flue gas will contain sulfide, nitrogen oxides, dust and other pollutants;


The flue gas treatment of the three heating furnaces in Wenfeng, Tangshan adopts the method of SDS (baking soda)+dust removal+SCR denitration. The desulfurization, dust removal and denitration system is constructed by Shanghai Xuanding Metallurgical Technology Group Co., Ltd. The system has been put into use since June 2021;


In order to better meet the requirements of environmental protection, solve the environmental pollution caused by sodium salt by-products of sodium bicarbonate desulfurization, respond to the national ultra-low emission policy and adhere to the principle of "green water and green mountains are golden mountains and silver mountains", Wenfeng Iron and Steel Co., Ltd. took the lead in carrying out calcium based transformation and calcium based superfine powder replacement of bicarbonate;


Based on the favorable conditions of previous general contracting, Shanghai Xuanding Group has considered the possibility of using bicarbonate of soda and calcium based superfine powder at the beginning of the system design. With the strong support of Wenfeng Steel, Shanghai Xuanding Group has undertaken relevant work. At present, the calcium based superfine powder (instead of bicarbonate of soda) system has been put into use, with excellent effect indicators;


3. Application of calcium based desulfurization (instead of baking soda) in coking industry


图片 4.png


In the production process of the coking industry (coke dry quenching, etc.), the sulfide in the flue gas needs to be treated. At the same time, the flue gas temperature is very low before the secondary dedusting, so the baking soda heating leads to higher energy consumption, and the large amount of consumption leads to more impurities in the by-product coke powder, which has low economic benefits;

Calcium based superfine powder is widely recognized and applied because of its wider temperature adaptation range (almost unaffected by the low temperature), significant reduction in consumption (about 30% reduction), and improved economic benefits of by-product coke powder;

Tangshan Dafeng Coking Co., Ltd. has a 140t/h CDQ system;


1. Feeding of CDQ equipment and facilities and calcium based superfine powder

1667800555796780.png  1667800561277707.png

2. Application effect of calcium based superfine powder

It can be seen from the automation screen that the flue gas temperature (at the inlet of the dust remover) is about 40 ° C, under which the sulfide emission index can be fully guaranteed;


1667800615215081.png  1667800631309375.png


In particular, it is worth mentioning that:

· Compared with baking soda, there is no need to raise the temperature, which saves a lot of fuel consumption and operation cost;

· Moreover, compared with other types of similar calcium based products on the market (low mesh size, low specific surface area), the consumption is more economical. From the statistics of projects that have been put into production, at least 30% of the raw material consumption can be saved, which can meet the requirements of sulfide indicators;

· Moreover, for the coking industry, the consumption saving of calcium based superfine powder can not only save the operating cost of raw materials for the owner and bring economic benefits, but also significantly reduce the impurity content in the dedusting ash (i.e., the coke powder from the secondary dedusting), bringing more other benefits;

(The following picture is taken from the network)

1667800679291800.png

3. Application video of calcium based superfine powder in coking (CDQ):


4. Application of calcium based desulfurization in waste incineration industry

The flue gas treatment in the waste incineration industry is now widely used (the following picture is quoted from the network):

1667800775447181.png  1667800780873912.png

图片 12.png

1667800841481815.png


5. Features and advantages of Shanghai Xuanding Group

Since its establishment, Shanghai Xuanding Group, based on the traditional business (general contracting of furnace and kiln projects), has made every effort to carry out and practice the environmental protection business. Its furnace business department, environmental protection business department and smelting business department have worked together and closely connected to achieve the beneficial combination of process and environmental protection;


The core team members of the furnace division of Xuanding team have experienced hundreds of industrial kilns and are very familiar with the production process and technical parameters of the kilns;


The environmental protection business department of Xuanding team has always been committed to the specific implementation of flue gas treatment, desulfurization and denitrification projects, and is very familiar with and understand various process routes and forms such as fixed bed desulfurization/SDS desulfurization;


Based on the technical precipitation and accumulation of the furnace itself and the environmental protection process, and in view of the flue gas characteristics of the furnace, the improvement and replacement of the traditional environmental protection process route, namely SDS baking soda, has been the key subject of the Xuanding team in recent years;


After years of continuous exploration, laboratory pilot test and engineering case practice, we have finally completed the technical accumulation of calcium based direct injection technology, and completed the final proportion and mass production of calcium based materials, and there are already implementation cases with ideal results;


It is worth mentioning that Jiangsu Xuanding New Material, an environmental protection new material company under Shanghai Xuanding, is a production and processing base integrating the research, development, testing, mass production and final engineering application of environmental protection new materials such as calcium based desulfurizer, which can better ensure the material performance and quality, and provide maximum convenience for maintenance or material recycling that may be required;


Shanghai Xuanding Group

Prepared by Environmental Protection Business Department


Prime Metallurgy Technology Group

Telephone:+86 21 24259995

Fax::+86 21 24259992

E-mail:xdjt@shprimetech.com

Address:Room 101, Building 1, No. 396, Xinfu Road, Minhang District, Shanghai


ABOUT US

BUSINESS

CASE

Follow us

Copyright @ 2022 Shanghai Prime Metallurgical Technology Group Co., Ltd.

返回顶部 seo seo