GASIN - Environmental Consequences of the use of Ethylene Glycol in the Processing of Natural Gas in Nigeria | By Father Edward Osang Obi, MSP, STD, Ph.D.

Environmental Consequences of the use of Ethylene Glycol in the Processing of Natural Gas in Nigeria | By Father Edward Osang Obi, MSP, STD, Ph.D.

Wednesday, 02 March 2016 00:00
Published in Bulletin - Edition 1
Rate this item
(0 votes)

Introduction

Nigeria's potential as a major global gas supply and utilisation hub is high. Available statistics show that even without a dedicated gas exploration regime, Nigeria has at present the 7th highest proven gas reserves in the world, with 183 Trillion Cubic Feet. This is gas that has been discovered in the process of exploring for petrol. We also have the potential of realising over 600 TCF, which would place us at 4th position worldwide. 

The FGN believes that in order to realise and sustain this potential, the structure of the gas sector must support continued cost effectiveness in supply of all markets (domestic, regional and export), scalability of capacity and above all, must be fully liberalized and market driven. Hence, the Nigerian Gas Master-plan (NGMP) has been developed and presented to investors since 2008. Among others, this Master plan proposes franchising three major Gas Processing Facilities (CPFs), all located in the Niger Delta region – Western Delta, around the Forcados area; Central Delta, north of Port Harcourt; and South East Delta, between Uyo and Calabar. Each of these Facilities is expected to process at least 1000 MMscf/d (standard cubic feet per day), but in fact 2,500 MMscf/d of raw gas. Largely overlooked, however, is the fact that significant amounts of toxic waste will be generated on a daily basis. 

The purpose of this presentation is to show that from conception to full design, this Master-plan so far fails to take into consideration the safe disposal of, and probable environmental hazards associated with, these toxic by-products and after-effects of the dehydration of gas using chemicals. From all presentations to investors in the industry it has become clear that the logic of economic benefits to be gained predominates, and environmental consequences are not touched on. Apparently there is the fear of scaring off investors when environmental aspects are brought into the equation. For instance, nowhere in it has consideration been given to human persons that might be affected and impacted by this budding gas industry. 

The toxic by-products of this process, as I shall demonstrate, are many and varied, and may bear down directly on the human, animal and aquatic populations in the Niger Delta. My plea is for the inclusion in the overall architecture of the Master plan, and its implementation, a full Life-Cycle Cost (LCC) that indicates not only the initial Capital Expenditure (CAPEX) for building the plants, but also the Operational Expenditure (OPEX) from conception to final removal of these facilities when their lifespan is exhausted. I shall suggest that it makes more economic sense to invest now in available clean technology than be saddled with the burden of disposing toxic wastes later on. 

 

1. Process of Gas Dehydration 

When extracted from the ground, natural gas usually contains significant quantities of water and other water-based and organic compounds. This is called 'wet gas”. During production, transportation and processing, changes in pressure and ambient temperature can lead to water condensation, ice and/or gas hydrate formation, or corrosion in the facilities. Dehydration, therefore, is one of the major processes in any gas processing plant, and Ethylene Glycol (EG) has been the chemical of choice for this industrial process since the 1960s. 

EG on its own is a common industrial chemical which has no extreme hazardous properties. Due to its hygroscopic (water-absorbing) properties, its natural affinity for hydroxyl (-O-H-), or water based functional groups, EG is an economical way of stripping the gas of its associated water. Water (H2O), in the chemical structure H=O-H, where the O-H is the chemically active part, will be chemically bonded to the EG. Based on this, the lean EG will absorb water in a counter-current contact with the wet gas and consequently dry it, thanks to its hygroscopy.

In a gas processing facility this is done in a so-called glycol contactor. The dry gas rises up and is conducted through pipes for use elsewhere, or is liquefied for easy transportation; the associated water, now heavy with EG is, on the other hand, routed from the bottom of the contactor and removed. The process could well have ended here, but in order to avoid a permanent supply of fresh EG, operators have developed a re-generation process for the 'used' or water-heavy EG. The process itself is simple: the used or heavy EG is collected and heated to its boiling point in this system, and in that way the water (plus other associated -OH compounds) is released from the EG (i.e., boiled off). 

This water, now in vapour phase, is vented into the atmosphere via a stack or chimney, and what remains is almost pure EG, which can once again be returned and reused in the process. The entire process has a good efficiency rate, because common practise shows the requirement of fresh EG is limited to 5-10%. So, apparently this 5-10% is lost somewhere in the process, and this happens during each and every sequence, continuously. However, 90-95% of EG is saved, and is re-circulated via the contactor to the MEG-Regeneration Unit all over again. (Note some of the acronyms used in the literature - MEG: mono-ethyl-glycol, DEG: di-ethyl-glycol, TEG: tri-ethyl-glycol, and TETRA EG: Tetra-ethyl-glycol).

The problem, however, is that in boiling one adds heat (energy) to the system containing the used EG, which has already bonded with water. But EG also bonds with other components that behave similarly with water: components that also have an active -OH functional group, e.g. phenol, alcohol, etc., and consequently react similarly. These include also organic molecules, small ones like alcohols, but also bigger ones like phenols, etc. 

In other words, any chemical with an end-standing functional –O-H group could possibly react with EG in this process, in a similar way as water does. As energy levels are high due to the heating, the resulting mix will contain many variations, subject to nature's random occurrence. So a part of the loss, an estimated amount of 80% of it, will leave the regeneration system as a vapour, and a part will precipitate and settle in the system. The vapour part is referred to by process technologists as BTX, referring to Benzene-Toluene-Xylene. These BTX compounds are naturally very toxic, and leave the EG regeneration-system with the water-vapour vented into the atmosphere. The remaining 20% settles down in the MEG-regen-unit and forms a carcinogenic black tar residue, continuously. When the vented vapour (i.e. the 80%) ultimately cools off through ambient temperatures, the gaseous compounds may condensate and/or precipitate, and disappear into the groundwater, which may be in use for human consumption. 

BTX-compounds can go through the human skin, so breathing, bathing and washing will do the damage equally. One does not even need to drink the contaminated water to be affected. Breathing is not a pleasant option either, because the smell one perceives when approaching a MEG-regen-unit is very strong and penetrating, leaving one with the unmistakable impression that this cannot be healthy. The black tar, on the other hand, accumulates in the re-gen-system. At a moment in time, say bi-annually, this has to be removed lest it affect the efficiency of the system. The tar is extremely carcinogenic.

2. Toxic effects of EG and associated Compounds 

Once again, to regenerate the EG, one adds (heat) energy to the system. But this energy is also sufficient to have EG react with salts and create fur-like deposits in the boiling system, just like one gets magnesium and calcium-based deposits on a cooker/boiler when (hard) water is brought to boiling point. This energy can also cause other -OH-molecules to react to/with other substances as well, which may have accompanied the wet gas from the earth. Here a special group of so-called aromatic compounds comes to mind. These have an exceptionally reactive end-group. Phenol is the -OH-variant. 

  • Phenol and its vapour, according to Wikipedia (free online encyclopedia), are corrosive to the eyes, the skin and the respiratory tract. Repeated or prolonged skin contact with phenol may cause dermatitis, or even second and third-degree burns due to phenol's caustic and defatting properties. Inhalation of phenol vapor may cause lung edema. Furthermore, the substance may cause harmful effects on the central nervous system and heart, resulting in dysrhythmia, seizures, and coma. The kidneys may be affected as well. Exposure may result in death and the effects may be delayed. Long-term or repeated exposure of the substance may have harmful effects on the liver and kidneys. The substance is a suspected carcinogen. 
  • Phenol can lose its -OH to the EG, leaving Benzene behind. Again, Wikipedia states that short term breathing of high levels of benzene can result in death, while low levels can cause drowsiness, dizziness, rapid heart rate, headaches, tremors, confusion, and unconsciousness. Eating or drinking foods containing high levels of benzene can cause vomiting, irritation of the stomach, dizziness, sleepiness, convulsions, and death.
  • The major effects of benzene are chronic (long-term) exposure through the blood. Benzene damages the bone marrow and can cause a decrease in red blood cells, leading to anemia. It can also cause excessive bleeding and depress the immune system, increasing the chance of infection. Benzene causes leukemia and is associated with other blood cancers and pre-cancers of the blood.
  • Also Toluene and Xylene are formed. On these, it is clear from Wikipedia that inhalation of fumes, for instance, can be intoxicating, but in larger doses nausea-inducing. Toluene in particular may enter the human system not only through vapour inhalation from the liquid evaporation, but also following soil contamination events, where human contact with soil, ingestion of contaminated groundwater or soil vapour off-gassing can occur.

The toxicity of toluene can be explained mostly by its metabolism. As toluene has very low water solubility, it cannot exit the body via the normal routes (urine, feces, or sweat). It must be metabolized in order to be excreted. Xylene exhibits neurological effects. High levels from exposure for acute (14 days or less) or chronic periods (more than 1 year) can cause headaches, lack of muscle coordination, dizziness, confusion, and imbalance

  • Exposure of people to high levels of xylene for short periods can also cause irritation of the skin, eyes, nose, and throat, difficulty in breathing and other problems with the lungs, delayed reaction time, memory difficulties, stomach discomfort, and possibly adverse effects on the liver and kidneys. It can cause unconsciousness and even death at very high levels.

Studies of unborn animals indicate that high concentrations of xylene may cause increased numbers of deaths, and delayed growth and development. The principal pathway of human contact is via soil contamination from leaking underground storage tanks containing petroleum products. Humans who come into contact with the soil or groundwater may become affected. Use of contaminated groundwater as a water supply could lead to adverse health effects.

  • Worse still, there is scientific evidence that short and long term exposure to BTX has negative effects on the semen and accessory gonads of people, especially workers, exposed to them over long periods. A study carried out on rats, for instance, revealed that “a subacute exposure of male rats to a high level (2000 ppm) of toluene vapour can elicit mild toxic changes in the kidneys, thymus, and reproductive organs of males…. In male rats… ethyl acetate and xylene were reported to interfere with the functions of the testes and accessory reproductive organs” (Xiao et. al., 2001. Effect of Benzene, Toluene, Xylene on the Semen Quality and the Function of Accessory Gonad of Exposed Workers, Industrial Health 39, 206-210).

Note that the compounds so far named are formed during the required boiling process to regenerate EG, and it is the lost 5-10% that often reacts with other micro-molecules in the natural gas, increasing their boiling point, and making them impossible to break down. These will therefore ultimately remain as residue: a black carcinogenic tar that can only be incinerated at very high temperatures. The problem: nature uses process kinetics with the implication that adding energy like heat will result in a new stable compound at a higher energy level, and this means, to change the new compound, one must add even more energy. How much energy can humans generate in order to break down the stable compounds they might ingest/assimilate? Very little, indeed.

 3. Implications for Human Beings 

Now the human body can provide a limited amount of chemical energy to deal with strange chemical compounds, normally sufficient to deal with normal natural environmental compounds with average energy levels required to break them down. But if the body cannot provide sufficient energy, the high-energy-level compound stays untouched and is stored in fat-layers in the body, or worse: in the organs. And sometimes, these chemicals remain active and can react with internal body-compounds like enzymes and proteins and amino acids, which happen to be the basic building block of a substance called de-oxy-ribo-nucleic-acid, better known as DNA. 

Once the DNA starts to replicate via a duplication kinetic called t-RNA-polymerase, a chemical reaction triggered by an enzyme, it will duplicate the amino acids in sequence, and also affect any changed amino acid, which could ultimately cause genetic defects in humans as this duplication process is sensitive and fragile. These defects may be simple and of no consequence if they are not on a key-functional part of the DNA. But who can guarantee this? If, however, they happen to be on a key-part, serious defects can occur, and these will ultimately result in defects at birth, immediately affecting the health and ability of the new born one.

4. Arguing for Chemical-free Technology 

It must be borne in mind that our purpose is not to oppose the Federal Government's intention to exploit our vast resources of natural gas, as this is necessary to meet the cash-calls for reaching our developmental goals. At the same time, we know that development that does not factor in possible consequences for human beings is a contradiction in terms. 

This is why we wish to reiterate that all the above mentioned toxic effects arise only when EG is used in the process of gas dehydration/purification. But there is now tested technology that does not require the use of EG, a good example being that in use right now in the Afam Gas Plant, which feeds Afam Power Station. My point is, since we know this technology exists, and is already being used at least in one gas plant in Nigeria, why not replicate it in others as well? Prevention, as they say, is better than cure; so why do we not choose to avoid the toxicity of BTX wastes by making a safe technology choice now, rather than be saddled with the social and environmental impact, and the possible political fallouts of unsafe disposal of these carcinogenic wastes? So far the only reason militating against this is the economics of cost-saving and profitmaking. But I do not find this convincing, because if one looks seriously at the equation, we must base our economic model on LCC, life cycle cost. 

This means that the cost of a project must be calculated from the day of conceptual design to the moment of dismantling the plant, including operational expenses OPEX (i.e. proper waste removal during operation) and removal expenses (i.e. proper waste removal after operation), and not only capital expenditure CAPEX, or the initial cost for setting up a gas processing unit. My view is that if you take all the removal/disposal costs into consideration, even apart from the related environmental, social and political problems, new chemical-free technology will prevail in advantage over EG-dependent processes. 

5. Recommendations 

  • We are aware that the FGN has recently approved fifteen companies worldwide to bid for engagement in the implementation of its Gas Master-plan. [UPDATE: Indeed, only in the last two months, that is, in April 2011, Agip-Oando partnership have won the tender for the construction and operation of one of these mega facilities] 

While we see the need for these operators to be given the freedom of choice to design and build their gas processing plants in the most economical way, we also wish to urge the government to be firm in dictating in as clear terms as possible, that: 

o the use of environmentally friendly technology will prevail over the plant economics of the various operators;

o there will be a stringent regime of environmental regulations, including penalties to deter and/or punish environmentally unfriendly disposal of toxic wastes;

o the economics of waste disposal should be taken into account in the economic comparison of the total LCC (life-cycle cost) of the various technology concepts, in this way allowing a fair chance for new chemical-free technologies with different CAPEX/OPEX. 

  • Assistance on these regulations could be sought from European countries like Germany and Norway that already have well balanced procedures in place. These could be used as template for the Nigerian industry. Malaysia and Brazil too are good reference points among so-called emerging economies.
  • An existing, or new Federal watchdog could be trained to be aware of the effects of gas processing on the environment, and to insist on EIAs before, and Post Impact Evaluations after, the project. This knowledge could benefit other industries and projects as well. 

Nigeria cannot afford to produce its resources at the cost of its environment. China is a guiding example of nations that sought quick economic growth, and overlooked possible environmental consequences. They are living with those consequences now, and possibly paying a high price for the health of its citizens and remediation of their despoiled environments. That is one way the Nigerian economic growth strategy should not follow, because Nigeria is growing democracy whereas China can afford to brutalise its population into silence and acquiescence. Short term economics may suggest high revenues in the immediate and middle term future, but these revenues cannot meet the long term cost of cleaning the waste once they enter into the ecological system. As the people have no option to relocate, since no such space is available in Nigeria, preserving what we have is the only way forward.

 

Read 3666 times