Carbon dioxide emissions from industrial processes come from chemical reactions or physical changes in the production of cement, lime, steel and calcium carbide (except for energy activities).In 2019, China produced 300 million tons of lime annually, accounting for 70.75 percent of the world’s total.According to the China Building Materials Association released “China Building Materials Industry Carbon Emissions Report (2020)” : In 2020, the cement and lime industries ranked the top two building materials industry carbon dioxide emissions, respectively, up 1.8% and 14.3% year on year.In 2020, carbon dioxide emissions from the cement industry were 1.23 billion tons, up 1.8 percent year on year, with coal combustion emissions up 0.2 percent and industrial production emissions up 2.7 percent.In addition, the electricity consumption of the cement industry can be indirectly translated into about 89.55 million tons of CO2E. Carbon dioxide emissions from the lime-gypsum industry were 120 million tons, up 14.3 percent year on year, among which coal combustion emissions rose 5.5 percent year on year, and industrial production emissions rose 16.6 percent year on year.In addition, the electricity consumption of the lime-gypsum industry can be indirectly translated into approximately 3.14 million tons of CO2E. That adds up to about 20 percent of domestic carbon dioxide emissions.
In lime production, according to the quality requirements of desulfurized limestone, calculated according to the purity of 90%, each ton of lime calcined produces carbon dioxide ~ 400kg. To burn one ton of lime in a vertical kiln, about 140 kg of standard coal is used. If the calorific value of coal is 6000 kcal, it will increase by 15%, consume ~ 160kg, and emit 470kg carbon dioxide according to 80% carbon content. The combined CO2 yield of the two can reach 870kg.
In addition to building materials industry, lime is also widely used in flue gas purification field. In hazardous waste disposal industry, when lime is directly used for dry deacidification, the utilization rate is usually below 30%. In the waste-to-power industry, when lime is used for semi-dry deacidification, the utilization rate is usually around 50%. According to lime content > 85% calculation, this equivalent to the removal of a ton of sulfur dioxide requires about 2.1 ~ 3.5t of lime, the total emissions of carbon dioxide 1.8~3.0t.
When using sodium based dry deacidification, take the baking soda desulfurizer launched by Al Environmental Protection as an example, each ton of sulfur dioxide removal needs to consume 2.63t baking soda, release 1.38t carbon dioxide. Because baking soda is made by reaction of soda as raw material and recycled carbon dioxide in a ratio of 1:1, the actual release amount is reduced by 1/2, that is, the release amount is 0.69t.
Comparing the two methods, it can be seen that for each ton of sulfur dioxide removed, the sodium-based drying method can reduce carbon dioxide emissions by 1.1 ~ 2.3t compared with the calcium-based drying method. If the power consumption of lime, slavered lime and other pulverizing processes is added, the carbon dioxide reduction will be even more significant.
The actual annual capacity of our municipal solid waste incineration plant has increased to more than 110 million tons. According to the estimate of 6 ~ 10kg of slaked lime used per ton of waste incineration, the annual consumption is about 1 million tons. If it is replaced by baking soda dry deacidification, it can reduce carbon dioxide emissions by 1 ~ 2 million tons per year.In hazardous waste disposal, coal-fired power generation and other industries, a large number of slaked lime is also used in flue gas purification. With the increasing environmental protection requirements for lime mining, crushing and calcination facilities, more energy saving, environmental protection and emission reduction of sodium based dry deacidification will be applied in more industrial scenarios, which is expected to reduce carbon dioxide emissions by more than millions of tons.