Atmospheric emissions

Initial considerations

A refinery is a complex industrial installation in which various processes take place with different characteristics. Some of these processes involve the atmospheric emission of gases (SOx, NOx, CO2), Particles and Volatile Organic Compounds (COVs).

Minimising atmospheric emissions is one of the principal objectives of the design and configuration of Refineria Balboa. Employing the latest generation of technology is today one of the most important tools with which to achieve a significant reduction of emissions in any industrial installation.

As can be seen in the following diagram, emissions in a refinery stem principally from two types of processes:

In a conventional refinery, the use of fuels in the production and obtaining of energy accounts for practically all of atmospheric emissions. Thus a reduction in energy consumption through the choice and efficient use of fuel (gas or liquid) will result in a reduction of emissions.

Since the 1990s, refineries have reduced their energy consumption by 16% (Source: Guide to Best Available Techniques (BATs) in the oil refinery sector, Ministry for the Environment). Refineria Balboa, thanks to an energy efficient design, hopes to save nearly 25% of the energy used by refineries in the nineties.

As is clearly demonstrated in the table below, the type of fuel used is decisive in considerably reducing emission levels. The table shows the difference in the emission of contaminates according to fuel used and, observing the data, it is easy to appreciate the great advantage, from an environmental perspective, of gas fuel over liquid. It is worth noting in this area the drastic reduction of sulphur and particle emissions into the atmosphere, and the total non-emission of metals in combustion.

Refineria Balboa will only use gas fuel. In no other refinery in Spain is this the case and consequentially, Refineria Balboa hopes to be a reference in its care for the environment.

"Bubble" concept (Guide to BATs)

The "bubble" concept, as it is termed, is a regulatory tool employed in various European Union countries. It commonly refers to SO2 emissions but can also be applied to other contaminants. As can be seen in the diagram below the "bubble" focus on air emissions considers there to be one "virtual chimney" for the whole of the refinery.

Refineria Balboa will use this concept in calculating and informing the public about its atmospheric emissions.

SOx emissions

Sox emissions in a refinery, mostly in the form of SO2, stem from three principle sources (Guide to BATs):

1. Combustion in furnaces and boilers
2. FCC unit.
3. Residual gas in Sulphur Recovery Plants (SRP)

By employing the Best Technologies, Refineria Balboa envisages a design with the maximum energy integration possible, with an aim to minimising contamination levels. Additionally, it has taken on board the strategies proposed by the Guide to BATs for the reduction of emissions which, in the case of SOx, are the following:

• Reduce the sulphur content of fuel: Refineria Balboa will use as fuel both refinery gas, treated to eliminate sulphur compounds, and natural gas whose sulphur content is practically non-existent.
• Increase output of Sulphur Recuperation Plants (PRAs): If the capacity of a plant is over 50 t/day (which is true in the case of Refineria Balboa) a specific regulation (RD 430/2004) applies for the limiting of SO2 emissions, stipulating that SRP output be no less than 98.5%. The sulphur plant planned for Refinery Balboa will have an output of 99.7%, thanks to the same unit’s recuperation and treatment of residual gas.
• Exclusion of the FCC unit: The unit with the greatest potential for contamination in a refinery is the FCC. Refineria Balboa’s design does not include this type of process.

From 2008, according to RD 430/2004, the limits on SOx emission will be changed from 1700mg SO2/Nm3 (RD 1800/1995) to 35 mg SO2/Nm3, a considerable reduction for which other refineries will have to prepare, while Refineria Balboa has been designed with this limitation in mind.

NOx emissions

During combustion with air as an oxidising agent, a mixture of nitrogen oxides is formed, generically known as NOx, which is composed of 90-95% NO with NO2 making up the remaining part.

The BATs to reduce NOx emissions are classified into 2 subsections:

• Before combustion. Using fuels with a low nitrogen content.
• During combustion. Substitution of conventional burners with special ones known as "low NOx burners".

As well as using the least contaminating fuel, Refineria Balboa will incorporate the special burners which, on account of their large size with respect to conventional ones, are difficult to install in refineries already in use.

The legal limit imposed by RD 430/2004, which comes into effect in 2008, for the emission of NOx is 200 mg NO2/Nm3. The current limit set out by (RD 646/1991) is 250 mg/Nm3.

CO2 emissions

CO2 has no limit value either for emission or for inmission, as it is not a contaminant but rather a substance that contributes to the so-called "Greenhouse Effect" and as such it is controlled and regulated on a global level.

The European Union’s ratification of the Kyoto Protocol, means that, in the period 2008-2012 Spain is obliged to prevent its emissions of greenhouse gases (expressed as C02 equivalent) from rising by more than 15 % of the base year (1990). The following diagram shows the per capita emissions of each member state of the EU in the last available year. It can be observed that the figure for Spain is below the average.

Tonnes of CO2 equivalent by inhabitant and year

*Source: Ministry for the Environment.

The National Allocation Plan, designed to fulfil the new obligations in place, has set aside a reserve for newcomers, of whom Refineria Balboa is one, incorporating their emissions into the plan for the future.

Particle emissions

Particles emitted by refineries fall into two large groups:

• Particles produced during combustion in furnaces and boilers.
• Particles resulting from the handling of solid powders (coke).

As Refineria Balboa only uses gas as fuel, the subsequent particle emission is minimal and, furthermore, contains no metals. At the same time, the storage, grinding and handling of coke is done "wet", which significantly reduces emissions into the air.

The limit placed on particle emission used to stand at 150 mg/Nm3 (D 833/1975), but when RD 430/2004 came into effect it was reduced to 5 mg/Nm3 for gas fuel. Balboa will easily comply with this limit.

COV emissions

COV emissions in refineries have four main origins:

1. Leaks and spillages from the pipe and tank network.
2. Emissions from the residual water system (separators and treatment plants).
3. Loss in the form of evaporation from the storage tanks.
4. Vapours proceeding from the loading and transfer stations.

In order to reduce emissions of these contaminants, Refineria Balboa will adopt the strategies proposed by the Guide to BATs, which suggest a series of measures to combat each of the sources of emission:

• In order to prevent possible leaks and spillages from the pipe and tank network, reliable high quality low leakage valves and accessories will be installed, along with a Leak Detection and Repair (LDAR) program. Vents and discharges into the atmosphere will be prevented and eliminated by sending them to the torch system.
• With regard to emissions from the residual water system, Refineria Balboa will take the following action:

  • Reduce as far as possible the volume and level of contamination from the residual water system.
  • Equip the collection network with pump seals in the drains.
  • Minimise the exposure time for hydrocarbons separated in settling tanks and other separation devices.
  • Place mobile covers over the separation pools, preventing the build up of explosive atmospheres.
    
• With regard to losses through evaporation in the storage tanks, the following measures will be adopted:

  • Use the appropriate tanks for the product.
  • Install double seals on the tanks with floating ceilings.
  • Minimise the number of accessories in the tanks.
  • Include tank parks in the LDAR program.
  • Check the method of sample taking.
    
• Spanish legislation, taking up EU laws, regulates the transfer system in the gasoline distribution networks, a product which, because of its high volatility, is one of the most emission producing. In light of this fact the BATs opt for the recuperation of vapours, where possible, through various techniques (absorption, adsorption, membranes, etc.); loading and unloading tanks from the bottom and connecting vapour balance lines to the loading tanks.

In conclusion, Refineria Balboa believes that adopting these combined measures will result in a significant reduction of final COV emissions.