Defining Green Refining

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This article comes ahead of the 2nd Green Refining and Petrochemicals Forum, hosted by EPC Ltd in Dubrovnik, Croatia. Many of the following challenges and solutions will be discussed by industry experts from leading regional and international oil, gas and petrochemicals companies. Click here for more details.

INTRODUCTION

The environmental issues surrounding the Oil & Gas Industry are becoming increasingly important, with governmental pressure leading to ever stricter legislation on the reduction of CO2 emissions and the production and use of alternative fuels.

The Oil & Gas Industry is being encouraged by governments, action groups and by the media to go GREEN but what does that exactly mean?

How can we define Green Refining?

Green Refining is a general term and can cover a variety of areas – In the Oil & Gas industry the term Green refining can be associated to a number of sectors but all with a common goal --- reducing emissions (GHG, CO2, wastes) and as a result minimizing the industry’s negative impact on the environment.

Green refining touches a number of subjects, such as;

• ENERGY EFFICIENCY - TECHNOLOGIES, INNOVATIONS

          - Technologies for CO² Reduction
          - Improving Energy Efficiency

          - Cogeneration in Refineries
          - Low-Carbon Fuels

• EMISSIONS - CO2, GAS, LIQUID & SOLID

          - Strategies for Reduction of Emissions in Refining and Petrochemicals
          - Sources and Factors Affecting Refinery CO2 Emissions
          - Reduction of Other Types of Emissions (Gas, Liquid and Solid)

• CO² CAPTURE & SEQUESTRATION

          - Meeting the GHG Reduction Goals by Carbon Capture and Sequestration-CCS
          - Carbon-Capture Methods - Pre-Combustion, Oxycombustion &
            Post-Combustion
          - Captured CO2 Injection & Uses - Depleted Oil and Natural Gas Fields

• RENEWABLE ENERGY SOURCES including BIOFUELS

          - Bio-Fuels & Alternate Fuels - Development, their Future and Competitiveness
          - Electricity from Renewable Resources - Status, Prospects, and Impediments
          - Promoting Growth of Renewable Energy

When adressing Green refining one subject is at the forefront of all discussions – Green House Gas emissions and CO2 emissions in particular.

Green House Gas (GHG) & CO2 emissions have been one of the hottest topics so far in this millennium’s energy debate. The reason for the growing interest is obvious – the ever-increasing concern about the CO2 release to the atmosphere and its impact on global warming and climate change.

CO2 emissions account for over 70% of the global GHG emissions --- so the questions is what is being done by the Oil, Gas & Energy sectors to reduce these emissions and the different available options, including in term of:

• CO2 REDUCTION TECHNOLOGY SOLUTIONS 

• CO2 CAPTURE

• CO2 SEQUESTRATION

CO2 EMISSIONS – TECHNOLOGY SOLUTIONS, CAPTURE & SEQUESTRATION

Everyone is aware of the growing concern regarding the possible climate change due to increasing CO2 emissions and Green House Gases (GHG) as a whole.

CO2 emissions account for over 70% of the global GHG emissions.

Global GHG & CO2 emissions come from a variety of different sources;  of which the global power generation and processing industries are major contributors.

As the above figures show; the energy & power industries contribute significantly to these emissions; so what steps are being taken to reduce these emissions and why?

There are a several prominent drivers for the process industry to manage and reduce its CO2 emissions, and these are often attached to concern over climate change.

Looking specifically at Refineries, the management of CO2 emissions is rapidly becoming an important aspect in all stages of project implementation.

So what are the tools available to manage & reduce these CO2 emissions?

Technology Solutions: Making the right choice 

In the current climate there is an increasing number of projects whose aim is to minimise or reduce the carbon footprint of a new or existing facility --- for these types of projects it is vitally important to select the best technology solution to reduce CO2 emissions.

Independently of how far reaching the emission reductions aims may be, applying an appropriate roadmap tool ensures that the most appropriate project to achieve the those goals is developed. 

CO2 Management Technology Options 

A well-planned design, processing the optimal feedstocks, with energy integrated flow schemes and a high value product slate is more likely to result in an efficient plant, whilst minimising energy demand and waste streams.

However, there are without fail always some unavoidable energy demands and carbon emissions. The following section introduces some of the key options for reducing greenhouse gas emissions, focusing on carbon dioxide (CO2) since it is the largest single contributor to the greenhouse effect, emitted from most operations in the process industry.

In other industries; other types of GHG are considered, notably carbon monoxide, methane, nitrous oxide and CFC emissions.

Grassroot (New) development projects have the advantage of being able to design their units for reduced CO2 emissions through both careful process selection and by also choosing the most appropriate primary source of energy.

However, both new and existing plant developments are able to look at the following options:

• Energy Efficiency

• Feedstock replacement

• Carbon capture and storage 

1. Energy Efficiency 

The most cost-effective solution to carbon abatement is improving site energy efficiency which can be applied to both existing and in-design plants.

By maximizing efficiency the overall carbon emissions and plant energy requirements will be minimised.

To evaluate and quantify the possible gains in energy two types of studies need to be performed:

• Process Efficiency Study

• Energy Efficiency Study

Process & Energy Efficiency 

The 1st study focuses on emissions which are generated by the process itself, such as CO2 emissions resulting from reactions within said process.

The energy efficiency section will focus on the minimising of the process heat & electrical energy requirements so that emissions from utility supplies may also be minimised.

Energy integration across any site can reduce the need for energy input to the plant – if we consider the addition of a new process unit, this may provide a source of waste heat which can be utilized elsewhere in the refinery and as a result eliminate the need for continuous use of a process heater elsewhere.

It is important to note that the process plants must maintain good operability -- able to start up independently and maintain availability.

However, if the plant in question is able to operate with fewer process heaters in operation, then clearly the energy demand of the plant will be reduced.

2.    Feedstock Replacement

In certain applications it may be possible to consider replacing (totally or partially) high carbon content feedstock with feedstocks which are closer to being carbon neutral.

For example: Gasification of coal / petcoke to produce a syngas.

Partial or full replacement with an appropriate biomass may be feasible in order to reduce overall carbon footprint, or increase production without increasing CO2 emissions.

3.    Carbon Capture and Storage  

Carbon Capture & Storage (CCS) is one of the most talked about issues in the industry’s drive for a greener outlook - CCS is the process of removing or reducing the CO2 content of streams normally released to the atmosphere and transporting that captured CO2 to a location for permanent storage.

Carbon capture and storage has the advantage of being applicable to almost all processes in some form or another.

Taking a closer look at the options for carbon capture and storage for CO2 emissions management: CCS can be applied to a wide range of large single-point sources, such as process streams, heater / boiler exhausts and vents from a range of high CO2 footprint industries including;

• power generation

• refining

• natural gas treating

• chemicals & cement production

 There are three main types of technologies employed:

• Pre-combustion capture

• Post-combustion capture

• Oxyfuel combustion capture

Once captured the CO2 is compressed, dried and transported to a suitable storage location such as saline aquifer, depleted oil field (where enhanced oil recovery could be employed) and depleted gas fields. 

Each CCS route described below is really a group of technologies based on similar process circumstances. 

A.    Pre-Combustion CO2 Capture 

Brief Process Description 

The feedstock (solid or gaseous) is fed to an oxygen (or air-blown) pressurised gasifier where it is converted to syngas. The syngas is then passed through a shift reactor which increases the hydrogen and CO2 content of the syngas. This high-pressure, high-temperature syngas is cooled, before being solvent washed to absorb the CO2 -- leaving a relatively pure hydrogen stream. The CO2 rich solvent stream is regenerated to release a CO2 stream which can be dried and compressed for export. 

Advantages 

This process offers an interesting integration potential as it generates a pure high-pressure hydrogen stream and the syngas cooling train produces significant quantities of steam (HP, MP, LP). 

Applications 

Possible application of pre-combustion carbon capture would be a new power plant in which the hydrogen rich stream is combusted in a gas turbine and the steam raised during syngas heat recovery is utilised, along with heat recovered from the gas turbine exhaust, in a steam turbine to form a combined cycle plant such as an IGCC (integrated gasification combined cycle). 

Variations 

• Coals, petcoke, fuel oils, municipal solid waste and biomass can be used as gasifier feedstock. 

• Natural gas and light liquid feedstocks can be used with a reformer.

• A range of alternative technologies such as membranes and pressure swing absorption (PSA) 

B.    Post-Combustion CO2 Capture 

Brief Process Description 

Combustion flue gas is cooled by direct water contact before entering a blower designed to overcome the absorption system pressure drop. The flue gas enters the absorption column where it is washed with a physical solvent such as monoethanolamine (MEA). 

The flue gas is scrubbed of up to 90% of its CO2 content and is returned to the combustor stack and released to atmosphere. 

The CO2 rich solvent is heated against lean solvent and regenerated in a stripping column. The solvent then returns to the absorption column while the released CO2 is dried and compressed for export. 

The highlight of the post-combustion process is that it is suited not only for new installations but also may be retrofitted to existing plants. 

Applications 

Post combustion carbon capture is typically associated with large retrofit power projects or new high carbon footprint power plants. Post-combustion CO2 capture is a simpler system than the one implemented in pre-combustion CCS and can be associated to almost any type of combustion system. 

Variants:

• A range of processes exist utilising different solvents: MEA, ammonia and even sea water.

• For high sulphur feeds the process may be coupled with a flue gas desulphurisation unit allowing the direct contact cooler to be eliminated.

C.    Oxyfuel Combustion CO2 Capture 

Brief Process Description 

Fuel is combusted with oxygen from an air separation unit. The temperature in the boiler is adjusted by recycling a part of the flue gas back to the combustion chamber. The flue gas passes through a selection of extractive equipment:

• particle removal by electrostatic precipitator

• sulphur removal by limestone scrubbing

• water removal by cooling and condensation 

The remaining flue gas has a high concentration of CO2 which can then be purified, dried and compressed for export. Steam from the boiler is used to generate power via a steam turbine. 

Applications 

The most common application of oxyfuel carbon capture is for new, large scale power production. 

Variants

• A wide range of fuels can be used in an oxyfuel flowscheme.

SUMMARY 

Environmental issues will continue to be at the forefront of the challenges facing the Oil & Gas Industry. It will be important to maintain the level of research & development into means of reducing emissions, increasing energy efficiency and exploring all possible renewable energy sources.

The 2nd Green Refining & Petrochemicals Forum to be hosted by Euro Petroleum Consultants next June in Dubrovnik (17th June 2011) will address many of these key topics in addition to latest technologies, issues, trends, regulations and strategies for reducing greenhouse gas emissions, including:

• Energy Efficiency Improvement

• CO2 Capture & Sequestration

• Renewable Energy Sources Including Cogeneration

• Biofuels Technologies

Visit www.europetro.com/Green_Forum_2011 for more information.