How technologies work to control pollutant emissions in agriculture

Concern about preserving the environment is a growing issue in all branches of the economy. For the Brazilian agricultural machinery market, the direction was no different. Conama resolution 433, of July 13, 2011, established two stages for compliance with this resolution, so that, in 2017 (stage 1), agricultural machines with power equal to or greater than 75kW should already meet the limits of the phase MAR-I, as well as, for 2019 (stage 2), machines with power between 19kW and 75kW also had to meet these same limits.

In this way, some new technologies were introduced into the market and will be presented below.

SCR SYSTEM

The SCR System (Selective Catalytic Reduction - Catalytic Reduction System) is basically composed of a catalyst. For this system we need a fluid composed of 32,5% high purity urea and 67,5% demineralized water, known in Brazil as Arla 32 (Automotive Nitrogen Oxide Liquid Reducing Agent).

This substance is injected (in spray condition), where, when mixed with combustion exhaust gases in the exhaust, it forms ammonia + nitrogen oxide (NH3 + NOx) before passing through the catalyst.

After passing through the catalyst, there is the formation of nitrogen (N2) and water vapor (H2O), plus exhaust gases within the established limits.

The SCR System is basically composed of a catalyst (which also acts as a silencer for the system), an Arla 32 supply pump, a tank, an Arla 32 injector, a temperature sensor (installed before the passage of the gases through the catalyst) and a NOx sensor (installed immediately after the gases pass through the catalyst).

Basically, all control of the SCR System and the diesel engine is carried out by an electronic management system (ECU).

EGR SYSTEM

The EGR System (Exhaust Gas Recirculation - Exhaust Gas Recirculation) consists of the technology of re-burning part of the exhaust gases, so that these gases, mixed with the intake air, will form part of the intake cycle of the next cylinder that will come into operation.

This recirculation causes the burning to have a lower combustion temperature and there is less oxygen, resulting in a smaller amount of nitrogen oxide (NOx).

Particulate matter management and control is carried out by controlling fuel burning (amount of fuel injected). For this emission control model, we have two models widely used in the market, the cEGR and the iEGR.

cEGR

The cEGR System (Cooled Exhaust Gas Recirculation - Recirculation of Cooled Exhaust Gases) consists of the technology of re-burning part of the exhaust gases. However, in this model, the gases go through a cooling process (in general, cooled by the engine's own coolant, where the heat exchange is done through a special radiator for the application) to later enter the cylinder's reburning.

All exhaust gases have a flow controlled by an electronic system and through a butterfly valve, it releases the gases into the environment or allows them to be directed to the intake of the next cycle. This system is generally installed next to the engine block.

iEGR

The iEGR System (Internal Exhaust Gas Recirculation - Internal Exhaust Gas Recirculation) consists of the technology of reburning part of the exhaust gases, mixed with the intake air, however, in this model, there is an internal route, in the engine block itself, that is, there is no type of cooling before the arrival of the next cylinder in the intake cycle.

This is considered the simplest model for controlling exhaust gas emissions. Externally, it is not possible to differentiate the engine without emissions control and with iEGR.

In the current market, there are machines with engines with mechanical injection (with injection pumps) and machines with electronic engines that use this technology (mechanical engines serve up to approximately 130 hp).

IMPORTANT POINTS BETWEEN SCR AND CEGR

Among machines with higher power, we can establish a comparison between the SCR System and the cEGR.

Machines with the cEGR System (system installed directly on the engine) stand out for having a system without additional items to the engine during installation and without the need to use Arla 32. However, machines with the SCR System stand out for promoting energy savings. fuel, as the entire operation to control emissions in exhaust gases is the responsibility of the SCR system, with an Arla 32 consumption between 3% and 5% (in relation to fuel consumption), allows the engine to work with few configuration changes .

IMPORTANT POINTS BETWEEN MECHANICAL AND ELECTRONIC ENGINES WITH IEGR

Among machines with lower power, we can compare engines with mechanical injection and engines with electronic injection (both with iEGR system).

Machines with mechanical engines with iEGR stand out for their lower acquisition cost and simplified maintenance, while machines with electronic engines with iEGR stand out for being more economical (fuel consumption up to 8% on average, lower when compared to engines mechanics with iEGR), agility of response in operation and guidance for maintenance assistance (guidance and warning for preventive maintenance and alarms for corrective maintenance).

The technologies existing on the national market offer different advantages, however, electronic engines with the SCR system offer a difference in economy and durability compared to the system that eliminates the use of Arla 32 (cEGR).

iEGR electronic engines have operational versatility when required for maintenance compared to mechanical engines.

 

 

André Rocha, AGCO