High-efficient nanotechnology and equipment for environmental recycling and water treatment
From the point of view of environmental and economic performance, created CSWP should operate on the basis of recycling all types of waste, which accompany the operation of the oil and gas industry, including oil-polluted waste (sludge), and related industrial and domestic waste (IDW), with obtaining of competitive products and services that are in demand in the operation of the enterprises and their infrastructure.
An important unifying factor for all types of waste is that the oil sludge and IDW contain components, sorting, and processing of which are not profitable and impractical, particularly in remote areas of Western and Eastern Siberia and the Far East. For example, the oil sludge contains solid impurities of large and small size that form a persistent emulsion, etc., making unprofitable process of their separation, and most of the standard methods of regeneration of oil sludge can not cope with the task. In economically developed countries, the trend is recycling of 70–80% of the IDW without sorting with cogeneration of heat and electricity, as well as (in small amount) with obtaining of materials for construction.
Thus, the concept of creating highly effective CSWP for the oil and gas industry should be based on innovative technologies, providing processing of wastes without preliminary sorting to produce heat, electricity and building material, as well as solving environmental problems at the present level. Innovative investment project "Highly efficient complex system of environmental waste processing for oil and gas industry" (Fig.1), which is formed on the basis of innovative technologies and equipment, meets these requirements.
Innovative technology for processing of all types of waste (oil sludge, industrial, domestic) is based on high temperature melting-gasification, and has a number of differences from other gasification or pyrolysis processes. High temperature processing of waste does not need pre-classifying of raw materials and is a cycle of the closed type, which eliminates all environmental risks associated with waste management. The only requirement is that the waste must comply with the size of the input window and must have a valid humidity. Mineral and metal contaminations are not only permitted, but encouraged.
Gasification is carried out mainly using technical oxygen and sometimes – water vapor. Depending on the factory size and characteristics of raw materials the processing efficiency reaches 75–80%.
The treated waste pass the following stages of processing at atmospheric pressure in the direct-flow reactor: drying, pyrolysis, gasification, partial oxidation, oxidation, partial oxidation and reduction (Fig.2). Gasification is performed in a reducing atmosphere at temperatures of 1 500–2 000 °C. A large part of the hydrocarbons is decomposed already in the reactor, making it virtually impossible the primary formation of dioxins and furans. When lowering down in the reactor column, the organic components of the waste are subjected to pyrolytic decomposition, enriching the flue gas. This pyrolysis gas is fed into high temperature area, where it is almost completely converted with oxygen as a gasifier. Organic compounds are decomposed into low molecular weight compounds at temperatures of about 2 500 °C.
Through the use of oxygen as the primary gasifier, a low content of nitrogen oxides (NOx) in the synthesis gas and the high calorific value of the latter (2–3 kWh/m3) are achieved. In conditions of destruction of organic materials and passivation, as well as of the concentration of inorganic materials, the hazardous substances are destroyed and recycled.
Thus, after the processing of waste using high temperature melting-gasification, virtually complete lack of products that require further disposal is achieved, i.e., dust and smoke are not produced in the environment. End products are gas, heat, stone, metal (Fig.3).
The offered technology and equipment allow to implement four main options for the use of the produced synthesis gas:
burning with water heating, electricity generation by the steam turbine;
production of heat and electricity using combined system;
partial conversion to methanol with associated heat generation during the synthesis;
transfer of processed gas to outside consumers.
The project envisages the creation of two variants of reactors with a capacity of 10,000 tons/year and 20,000 tons/year. Gasifying line consists of two reactors, and waste processing can continue even if you stop one of them for service. Thus, the gasifying capacity of the line is 20,000 or 40,000 tons/year. The modular structure allows to increase the complex’s capacity by installing additional gasifying lines.
"Self-sustainability" of the system allows to install it in the place that best meets the needs of the region or business. This energy source is able to allow inaccessible regions to become more autonomous. Recycling of one ton of waste provides about 1.6 MW/h of electricity, or about 380 liters of diesel fuel. Processing products are used in primary and secondary production of oil and gas companies, as well as in the social sphere.
The wastewater treatment system is created on the basis of universal technology of electrochemical activation (ECA). This technology enables the use of the same processes of synthesis of electrochemically activated solutions for water purification, as well as technical systems with the same type of electrochemical reactor for use in a variety of fields. The electrochemical systems are developed and manufactured with capacities from a few liters per hour up to several thousand cubic meters per day, which are used for high-quality purification and disinfection of drinking water, wastewater, etc. (Fig.4). Models for use in large water treatment plants and in individual cottages and apartments are developed and serially produced.
The main advantages of ECA over conventional chemical technologies are environmental friendliness, efficiency and versatility.
Environmental friendliness is caused by the possibility to completely eliminate or significantly reduce the use of chemical reagents in industrial processes requiring the use of water and aqueous solutions for various purposes, including in disinfection and purification of drinking water and also to completely eliminate or significantly simplify the purification of the sewage that is usually necessary at use of conventional chemicals.
Efficiency is caused by significant increase in the efficiency of processes by reducing labor costs, time and materials consumption, and by improving the quality and functional properties of final products.
The versatility of the ECA allows to create equipment for use in the project for drilling, mining, transportation and processing of oil and gas (Fig.5). For example, the ECA allows to reduce the amount of chemicals used in drilling on 60–70%; to increase the mechanical drilling speed in 1,5–2,0 times; to significantly reduce environmental pollution and contamination of aquifers due to nonchemical regulation of physicochemical parameters of drilling fluids (viscosity, water loss, static shear stress) and reduction of the critical area of formation thanks to the electroosmotic prevention of the penetration of mud filtrate into the formation, as well as through the use of electrokinetic removing of fine-dispersed solid phase (clay particles smaller than 10–20 µm in size) from a drilling fluid, which allows to exclude the operation of dilution of the latter.
Various modifications of electrochemical modular compact systems allow to synthesize the hydrochloric acid and caustic soda from sodium chloride solution. Energy consumption per ton of caustic soda does not exceed 3000 kW. Simultaneously with the production of one ton of caustic soda in the form of a 18% solution, 0.9 tons of hydrochloric acid with concentration of 15% (according to hydrogen chloride – 100%) is synthesized.
Electrochemical devices of various modifications also help to clean natural water and turn it into drinking at almost any source contamination. Capacity of a single installation can range from 20 to 500 liters/hour.
The intensification of the secondary methods of oil extraction can increase the oil recovery in case of injection of the electrochemical activated solutions by 5–10% in comparison with the displacement of the oil by aqueous solution of polyacrylamide or micellar solutions. At the same time, the consumption of chemicals is eliminated, in particular of surfactants, and contamination of the environment is prevented. The energy consumption of production of ECA solutions is 0.5–0.7 kWh/m3.
ECA can be used to solve the following tasks:
removal of asphaltene sediments using hot electrochemically activated water with the preset values of pH and oxidation-reduction potential (ORP) and addition of surfactants;
bactericidal treatments with a solution of oxidants from AQUATRON devices with the addition of the corrosion inhibitor or without it;
flushing of pipelines using solutions on the basis of electrochemically activated water for removing of asphaltene sediments;
flushing of wellbore zones for intensification of oil production using electrochemically activated water or bactericidal water-in-oil emulsions on the basis of electrochemically activated water.
In transportation of oil and gas the use of ECA for corrosion protection of pipelines against aggressive liquids (stratal, waste and sea water) eliminates the need for corrosion inhibitors, provides 99% protection when power consumption is 0.016–0.027 kWh for 1 cubic meter of pumped liquid. This prevents environmental pollution by inhibitors and corrosion products.
The preparation of solutions of scale inhibitors using electrochemically activated water with controlled pH and redox potential will provide decrease in a consumption of inhibitors in 3–4 times while maintaining performance of solutions.
ECA is efficient in electrical desalting of oil. Before feeding the crude oil to the refinery the excess of the dissolved salts must be removed by addition of water followed by separation in an electrostatic field. Replacement of normal water by a cathode activated allows to speed up the extraction of salts, to increase the depth of oil purification from salts in 3–5 times, to reduce the required amount of added water in 2–4 times.
Purification of associated gas from hydrogen sulfide in the process of pipeline transport of oil, purification of natural gas prior to obtaining the LNG by using an electrochemically activated solution of sodium sulfate allows to create waste-free, automated production that does not pollute the environment, to eliminate the use of costly absorbents and adsorbents (ethanolamines, zeolite), to reduce the loss of gas in 3.5–4.0 times compared to existing methods.
If to use the cathode-activated distilled water under pressure of 15 kgf/cm2 and with a temperature of 120 °C in the pyrolysis of straight run gasoline, then the output of basic products of organic synthesis (ethylene, propylene, butadiene, benzene) increases approximately twice.
Use of electrochemically activated potable water in the production of chromia-alumina catalysts for dehydrogenation of paraffin hydrocarbons (butane and isopentane) provides increase in activity and strength of the catalyst by 10%. The technology is developed by specialists of the Syzran plant for the production of catalysts with the participation of the authors of the ECA.
The technology of emulsion polymerization of butadiene with styrene with the use of electrochemically activated potable water allows to improve the efficiency of production of butadiene-styrene rubbers due to reducing the consumption of reagents (rosin soap, chloride and potassium pyrophosphate), to increase by 40% the rate of copolymerization, to improve the quality of the rubber. The technology is developed by scientists and specialists of the Kazan National Research Technological University and Nizhnekamskshina with the participation of the authors of the ECA.
In General, the domestic technologies and equipment allow to create a highly effective comprehensive system for ecological waste management in the oil and gas industry, which meets the modern requirements of the world market.