RU2540652C1 - Method for cleaning flue gases of thermal coal-fired power plants from mercury - Google Patents

Abstract

FIELD: power industry.

SUBSTANCE: invention relates to ecology in power industry. A cleaning method of flue gases of coal-fired boilers of thermal power plants from mercury, which involves introduction of activated coal as a sorbent, differs by the fact that the sorbent is obtained from alkali charcoal by its treatment with water vapour at the temperature of at least 800°C with further crushing and screening on a sieve with mesh size of not more than 100 mcm, with that, the method is implemented at the temperature interval of 110 - 120°C with introduction of the sorbent to flue gases immediately before ash collecting systems.

EFFECT: increasing cleaning degree of flue gases from mercury.

Description

Area of use

The invention relates to the field of ecology in the energy sector and can be used for purification of mercury flue gases from pulverized coal boilers of thermal power plants (TPPs). Ensuring environmental safety associated with atmospheric pollution with mercury-containing wastes is one of the most important environmental problems in the modern development of the heat and power industry. Pulverized coal power plants are the main source of mercury emissions into the environment. The UN Environmental Protection Program and the Arctic Council of the countries adjoining the Arctic have recognized coal-fired TPPs as the main and global anthropogenic source of mercury emissions into the environment. Emissions of mercury from coal-fired TPPs account for about 46% of total global anthropogenic emissions of mercury and about 44% of mercury emissions from the eight countries of the Arctic Council, with the United States and Russia making the largest contribution to these emissions. In 2001, 485 TPPs located on the territory of the Russian Federation consumed 124 million tons of coal, which, according to expert estimates, led to emissions of 8 tons of mercury in the atmosphere and to the accumulation of 2 tons of mercury in waste (“Estimating mercury emissions in the Russian Federation”, ACAP, 2006) .

State of the art

The most promising technology for the effective reduction of mercury emissions into the environment is the injection of sorbents into the flue gases at the outlet of the boilers. In this case, mercury is adsorbed on the sorbent and then trapped together with fly ash in ash collectors (RK Srivastava, N. Hutson, B. Martin, F. Princiotta, J. Staudt. Control of Mercury Emissions from Coal-Fired Electric Utility Boilers. Environmental Science & Technology 2006, 40, (5), 1385-1393).

The closest known technical solutions (prototype) to the claimed invention is a method for purifying flue gases from mercury by introducing into them a sorbent in the form of a dry mixture of powders of activated carbon and halogen salt (US 8409330, B01D 53/06, 04/02/2013). The disadvantage of this technical solution is that in order to achieve a high degree of mercury sorption, a complex composition and relatively expensive mixture is proposed.

Disclosure of invention

The task to which the invention is directed is the development of a relatively inexpensive and effective technology for cleaning mercury flue gases from coal-fired boilers of thermal power plants at temperatures in the range of (110 ... 120) ° C, and the achieved technical result is the possibility of using a cheap one-component sorbent, which in combination with temperature and other conditions of industrial use, a sufficiently high degree of purification of flue gases from mercury.

The indicated task and the technical result achieved according to the invention are ensured by the use of activated carbon obtained from alkaline charcoal by treating it with steam at a temperature of at least 800 ° C, followed by crushing and screening on a sieve with a mesh size of not more than 100 μm as a sorbent for trapping mercury in the temperature range (110 ... 120) ° C from the flue gases of coal-fired boilers of thermal power plants with the introduction of the sorbent into the flue gases directly in front of the ash collecting devices.

Practically, these conditions are satisfied by activated (active) coal produced by the domestic industry under the brand name OU-A (GOST 4453-74), which is a black powder with an absorbing surface of 1200 m ² in 1 g of coal.

Patentability Rationale

The claimed invention meets the criterion of "novelty", since in the well-known scientific, technical and patent literature there is no complete set of features characterizing the invention. In the indicated literature, in particular, there are no data on the possibility of effective sorption of mercury at high temperatures by activated carbons without their special treatment or mixing with other components.

The claimed invention meets the criterion of "inventive step", since the possibility of using, in a certain way, the obtained activated carbon in pure form as an sorbent for capturing mercury from flue gases at a temperature of more than 100 ° C was first discovered when the claimed invention was created and does not follow for a specialist in the field in an explicit manner from the prior art.

The claimed invention meets the criterion of "industrial applicability", as it can be used in an industrial environment for the purification of flue gases from mercury.

Examples of using

The invention is illustrated by examples of using the inventive method for capturing mercury at elevated temperatures in a laboratory setup and a pilot plant based on TPPs.

Example 1

A sorbent — activated carbon of the OU-A grade according to GOST 4453-74 under conditions similar to the use of this technology in a real pulverized coal-fired power plant — was tested at a laboratory installation: the concentration of the sorbent in the gas stream is 150 mg / m ³ with a total mercury concentration of 30 μg / m ³ , temperature (110 ... 120) ° C and capture of particles of the sorbent with absorbed mercury at a distance of not more than 1 m from the place of its introduction into the flue. The efficiency of capturing mercury with activated charcoal OU-A grade under these conditions amounted to (75 ... 80)%.

Example 2

For comparison, in the conditions of example 1 was tested standard sorbent complex composition of the company Albenarle (Albemarle), which is widely used in the United States at TPPs (application US 2011/0162524, publ. 07/07/2011). The efficiency of mercury capture by coal of the specified company in these conditions also amounted to (75 ... 80)%.

Thus, the use of activated charcoal of the OU-A grade as an sorbent for capturing mercury from flue gases under conditions limited by the claims below gives unexpected high results for capturing mercury at relatively high temperatures without special treatment and mixing with other components. This allows you to significantly reduce the cost of the cleaning process by replacing special expensive sorbents with cheap domestic activated carbon, which can be produced in the immediate vicinity of the thermal power plant.

Claims (1)

A method of purifying flue gases from pulverized coal boilers of thermal power plants from mercury, including the introduction of activated carbon as a sorbent, characterized in that the sorbent is obtained from alkaline charcoal by treating it with water vapor at a temperature of at least 800 ° C, followed by crushing and screening on a sieve with a size cells not more than 100 microns, while the method is carried out in a temperature range of 110 - 120ºC with the introduction of the sorbent into the flue gases directly in front of the ash collecting devices.