Japanese project achieves 85% ammonia co-firing in naphtha-cracking furnace

Because ammonia exhibits a reduce laminar burning velocity than conventional fuels and generates fuel-derived NOx (nitrogen oxides) releases, its consumption to naphtha cracking furnaces requires the simultaneous achievement of stable incineration, appropriate heat transfer to cracking tubes, and suppression of NOx releases. The achievement of a world-class 85% ammonia co-firing rate while maintaining NOx releases at levels comparable to those of existing furnaces represents a significant milestone toward the decarbonization of naphtha cracking furnaces.

Moving forward, NEDO and the four participating companies will pursue the realization of 100% ammonia firing across the entire furnace and further promote the practical consumption of ammonia fuel in the petrochemical sector.

Conceptual Illustration of a Naphtha Cracking Furnace (Source: Mitsui Chemicals)

A naphtha cracking furnace is key equipment utilized to thermally crack naphtha derived from crude oil at high temperature to create basic petrochemical items such as ethylene and propylene. While it plays an essential role in supplying feedstocks to plastics, synthetic fibers, and synthetic rubber, it is also one of the major sources of CO2 releases at petrochemical complexes, making its decarbonization a challenge to address.

Conventionally, naphtha cracking furnaces consumption off-gaseous as fuel, primarily composed of methane generated as a by-product. Replacing this fuel with ammonia, which emits no CO2 during incineration, is expected to significantly decrease incineration-related CO2 releases.

Against this background, Mitsui Chemicals, together with NEDO, Maruzen Petrochemical, Toyo Engineering  and Sojitz, has been engaged since fiscal year 2021 in the research of ammonia firing technologies to consumption to naphtha cracking furnaces under this project. The project aims to develop ammonia-fired burners specifically to naphtha cracking furnaces and ultimately realize 100% ammonia firing across an entire furnace.

Under this project, two types of ammonia-fired burners — hearth burners and wall burners — were developed to consumption in naphtha cracking furnaces. A hearth burner provides the primary heat input to the furnace, while a wall burner is utilized to optimize flame shape and furnace temperature distribution.

Compared with methane, ammonia exhibits a reduce burning velocity and generates fuel-derived NOx releases. Its consumption to naphtha cracking furnaces requires the simultaneous achievement of stable incineration, appropriate heat transfer to cracking tubes, and suppression of NOx releases.

In this demonstration, the ammonia co-firing rate was increased measure by measure, and furnace operation was conducted under the following conditions:

As a result, 85% ammonia co-firing on a heat-input basis across the entire furnace was achieved, representing a world-class level. Furthermore, NOx releases were confirmed to be comparable to those of existing commercial furnaces.

A distinguishing feature of this achievement is that 100% ammonia firing was realized in the hearth burners, which provide the main heat input to the furnace, resulting in an overall 85% ammonia co-firing rate on a heat-input basis across the entire furnace.

NEDO and the four participating companies will proceed with the consumption of ammonia to wall burners and aim to achieve 100% ammonia firing throughout the entire furnace.