LT6798B - A method of using bottom ash and slag for cleaning combustion gases - Google Patents

Abstract

The invention relates to a method for cleaning gaseous pollutants, specifically for the sorption process by the waste incineration bottom ash, to reduce the concentration of carbon dioxide (CO2) in gaseous combustion products. The object of the invention is to provide a method for purifying (reducing) gaseous pollutants (CO2) during the combustion process, by using waste incineration bottom ash as an effective sorbent filler, which could be used in civil engineering after exploitation. This technology has two main advantages: carbon dioxide is removed from the gas; insoluble calcium carbonate (CaCO3) is formed during the carbonation reaction, when the reaction of calcium oxide (CaO), carbon dioxide (CO2) and water vapor (H2O) takes place. CaCO3 acts as a binder during the bottom ash stabilization process, preventing heavy metals from leaching. Waste incineration bottom ash is used as a sorbent material; the concentration of calcium oxide (CaO2) in bottom ash is not less than 20%; the particle size of bottom ash reaches 0-11.2 mm and humidity - 20%.

Description

FIELD OF THE INVENTION

The invention relates to a process for the purification of gaseous pollutants, in particular to a sorption process of waste bottom ash and slag in order to reduce the concentrations of carbon dioxide (CO2) in gaseous combustion products.

BACKGROUND OF THE INVENTION

Climate change is a major risk facing humanity. Emissions of CO2-based greenhouse gases (GHGs) into the atmosphere cause the atmospheric temperature to rise. CO2 enters the atmosphere due to natural processes as well as anthropogenic activities. The main sources of CO2 emissions are transport and energy facilities burning fossil fuels.

However, scientists have found that despite all the measures to reduce CO2 emissions that are already in place in the world, atmospheric CO2 concentrations are increasing by about 2 ppm per year. A sufficiently deep understanding of the sources of CO2 emissions is needed to ensure a reliable forecast of climate change. China accounts for the largest share of GHG emissions, and the country's government has decided to reduce GHG emissions by 45% by 2020 compared to 2005 and by 65% by 2030. EU by 2020 intends to reduce emissions by 30% if other economically strong countries commit to make a fair contribution to the global effort.

Currently, the following main methods of gaseous pollutant purification are used: catalytic, biological, sorption. Economic and operational indicators must be taken into account when designing the treatment system, therefore filters-absorbers are a viable alternative to catalytic and biological gaseous pollutants. Sorption methods are divided into: physical absorption (with water), chemical absorption (with alkaline hydroxides, alkaline carbonates, ethanolamines), removal by membranes or molecular sieves.

The task of modern sorption treatment methods is to increase the efficiency of gaseous pollutant treatment. To achieve this goal, it is expedient to use waste generated during the energy production process, which has a high sorption capacity of gaseous pollutants (ash and slag from the bottom of waste incineration).

One of the main problems of sorption cleaning technologies is the high cost of sorption filter fillers and / or the complex pre-treatment / production process and low recycling potential.

The prototype of the present invention is a method of producing a CO2 sorbent and a method of its application (Russian Federation Patent No. 2451542 "ilomoTMTenb flnoKCMfla ymepofla, cnoco6 ero nonyMeHMH (BapnaHTbi) m cnoco6 ero nonyneHH ^"). The sorbent preparation method described in the prototype involves several steps:

For the removal of carbon dioxide from gas mixtures, the currant contains 4-70% calcium oxide and 29-95% yttrium oxide.

Yttrium oxide is impregnated with a solution of soluble calcium compounds, or by mixing with calcium compounds. The resulting material is dried and calcined at a temperature of 1000 ° C;

Gaseous pollutant flow humidity can reach up to 100%, flow temperature - 550850 ° C, gas pressure - 1-30 atm.

The sorbent can be used in thermal energy.

The described prototype has several shortcomings:

Yttrium extraction is a complex and expensive process because metallic yttrium is obtained by reducing anhydrous yttrium halide with lithium or calcium followed by distillation of impurities;

Sorbent components must be further treated at high temperatures, which requires high electricity consumption.

The possibilities of reusing the used sorbent (in the construction, road construction sector) are limited.

SUMMARY OF THE INVENTION

The object of the invention is to develop a method for the purification (reduction) of gaseous pollutants (CO2) from the combustion process, using ash and slag from the bottom of waste incineration as an efficient sorption filter filler, which can be used in civil engineering after operation.

According to the present invention, the bottom ash and slag from the incineration of waste (after partial separation of the metals using an electromagnet) are taken from the incineration plant, from the bottom ash and slag storage room. The power plant incinerates non-reusable or non-recyclable waste at a temperature of at least 850-1050 ° C.

The use of bottom ash and slag particles of different sizes reduces aerodynamic drag and improves filtration properties.

This technology has two main advantages: it removes unwanted carbon dioxide from the gas; the reaction with calcium oxide (CaO), carbon dioxide (CO2) and water vapor (H2O) undergoes a carbonation reaction to form insoluble calcium carbonate (CaCOs), which serves as a binder in the bottom ash and slag stabilization process, preventing the leaching of heavy metals.

DETAILED DESCRIPTION OF THE INVENTION

Preparation of sorption filter filler

The bottom ash and slag are cooled by watering, so a sample of the dry bottom ash and slag mass must be dried. The bottom ash and slag are dried in an oven for at least 24 hours at a constant temperature of 105 ° C.

The dried filler is stored in sealed plastic containers to protect against possible adverse environmental effects or contamination of samples.

To obtain a properly sized particle filler, dry bottom ash and slag are sieved through an 11.2 mm mesh sieve. A vibrating sieve shaker is used to facilitate the separation of the fractions. Bottom ash and slag can also be shredded using a gill shredder.

Use of filler for combustion process gas cleaning

CO2 removal from gas is based on hydration and carbonation reactions:

CaO + H ₂ O Ca (0H) ₂ (1)

Ca (OH) ₂ + C0 ₂ - »CaCO ₃ + H ₂ O (2)

The conversion of calcium monoxide to calcium hydroxide (formula 1) in the combustion chamber is of particular importance for the processes. Upon contact with carbon dioxide (CO2), a carbonation reaction begins (formula 2). First, carbon dioxide is absorbed in the water in the bottom ash and slag pores, then calcium carbonate (Ca (OH) 2) reacts with dissolved CO2 (water required for the reaction) to form calcium carbonate. As the removal of unwanted carbon dioxide from the gas requires water, the filler (moisture content of the bottom ash and slag) must be 20%. To achieve proper humidity, the bottom ash and slag are saturated with water.

In order to achieve efficient CO2 removal, bottom ash and slag must contain a high concentration (> 20%) of calcium oxide (CaO).

Research shows that 1 tonne of bottom ash and slag (0-40 mm particle size) from the waste incineration process can trap about 10.9 kg of CO2.

The smallest fraction (0-2 mm), which has the largest surface area, has the highest CO2 sorption (removal) capacity (almost 35 kgCO2 / tdp). Although the sorption capacity decreases with increasing particle size of bottom ash and slag particles, too high aerodynamic drag reduces the efficiency of the method. To ensure the efficiency of the method, 0-11.2 mm bottom ash and slag particles are used for the sorption filter filler.

DESCRIPTION OF THE DRAWINGS AND FIGURES fig. shows an image of different fractions of bottom ash and slag particles used in the combustion process gas cleaning process as a sorption filler.

DESCRIPTION OF THE IMPLEMENTATION OF THE INVENTION

The implementation of the method of using waste bottom ash and slag for gas cleaning in the combustion process starts with the process of treating waste bottom ash and slag, during which the fraction of 0-11.2 mm particles is separated. Using the prepared material, filter cartridges are produced or containers filled with sorption material through which the combustion products will be filtered.

This combustion process gas cleaning method can be used in small boiler houses or individual houses to reduce the CO2 concentration in gaseous combustion processes.

Claims (1)

DEFINITION OF THE INVENTION 1. A method of using waste bottom ash and slag for the cleaning of combustion process gases in order to reduce the concentration of carbon dioxide CO2 in gaseous combustion processes, characterized in that: uses ash and slag from the incineration of waste as a sorption material for the method; the concentration of calcium oxide (CaOz) in the bottom ash and slag is not less than 20%; bottom ash and slag particle size 0-11.2 mm and moisture 20%.