Technology creation of water-coal fuel suspension based on Uzbekistan’s coals

Topicality and demand of the subject of dissertation. Owing to decreasing of reserves of oil and gas and also increasing of their cost on the world market, the role of solid fuel in fuel and energy balance of Uzbekistan has increased. However, ecological problems, rising at using of coal fuels have demanded for elaboration and introduction of new ecologically pure coal-fuel technologies. The same developed technology connected with coal using as fuel in form of water-coal fuel suspension (WCFS) has been advanced manufacturing recently in world practice. Combustion of coal in form of WCFS has some economical, ecological and operational advantages in comparison with powdered and layered combustion. Using of WCFS has allowed to increas effectivity of coal combustion, to utilize coal slimes, to decrease of explosion - danger of coal dust in energy boilers, decreases amounts of sulfur and nitrogen oxides emissions into the atmosphere. Introduction of relative cheap WCFS in practice promoted saving of energetical and material resources and limiting of environment pollution.
Taking into account above mentioned of WCFS advantages in comparison with modern types of fuel and also availability for it creation of cheap and local raw materials, development of new stable WCFS obtaining on the basis of Anhren and Shargun coals, as well as them rational combustion in different furnace aggregates instead mazut and natural gas can be used one of the perspective trend of energetic elaboration and coal industry of Republic.
The present dissertational work is focused on the implementation of the resolutions of the President of the Republic of Uzbekistan the NPR-1442 dated December 15, 2010 «On the priorities of industrial development of Uzbekistan for 2011-2015» also Cabinet of Ministers of the Republic of Uzbekistan dated October 30, 2013 N292 «Development economy and management by coal industry rising qualitative level of developed new produce for account of design and exploratory and research works, dated June 6, 2013 year, N161 «Growth of coal industry for account of realization of priority investment projects directed to meet the growing population needs in coal industry for 2013-2018» which directed to accelerate implementation of modern scientific achievements and progressive innovative technology of WCFS based on Uzbekiston’s coals in the manufacture fields.
Purpose of research is consisted in development of technology of new types of fuel - WCFS based on coals of Uzbekistan; and their using in furnace aggregates of industries.
Scientific novelty of the dissertation research consist in the following:
physico-chemical properties (humidity, ash content, volatile substance content, carboxylic and hydroxyl groups, heating capacity) of Angren brown and Shargun black coals, were determined rheological properties of WCFS obtained based on low-ash and high-ash coals such as Angren brown and Shargun black coals were defined;
optimal amounts of stabilizing and plasticizing additions (NaOH, Са(ОН)з, SAS) for WCFS were found. When addition of stabilizers NaOH and Ca(OHh in the ranges 0,5-2,0% from initial weight of fuel, its viscosity increased, but dynamic stress of displacement is reduced, the viscosity of WCFS decreased in 1.5-2.0 times, and dynamical strain of displacement is increased in 2.0 times at rising of temperature from 20°C to 60°C respectively;
it was reveiled that viscosity the WCFS obtained based on brown coals is several more than the WCFS obtained based on black coal, e.g. if this value for WCFS, obtained based on sort of 2BPK is 2.52 MPa s, as WCFS from black coal sort of 1SSKOM will be 1.84 MPa s;
for fuel, dispersion phase which consist of particles up to 50 pm (80%), the influence of dispersion phase content to structural viscosity values, stability and burning was found. It is established that solid phase content is 38-40, 44-46, 49-51 and 52-55%, respectively in the WCFS obtained coals based on 2BPK, 2BOMSCh-Bl, 2BOMSCh-B2, and 1SSKOM;
stable and high caloric WCFS were obtained by mazut modification (which is contented 4-16% from initial weight of fuel) of Angren brown coals, sorts of 2BPK, 2BOMSCh-Bl and 2BOMSCh-B2. It was shown that heating capacity of WCFS based on 2BPK in optimal condition is 2900 kcal/kg;
the optimal regimes of technology proportional and full combustion of WCFS were worked out basis of the using new jumbo burner allowed delivery of heat pretreatment fuel and compressed air in the furnace aggregates.
CONCLUSION
1. For the first time possibility effective using low-and high-ash brown coals from Angren and Shargun deposits of the Republic of Uzbekistan has been sounded with purpose obtaining instead liquid fuel oil the alternative water-coal fuel suspension (WCFS), as well as existing optimal regime technology has been tested for normal and full their combustion with using new jumbo burner with pretreatment heating of fuel and compressed air.
2. Technology of WCFS obtaining based on of Angren coals of sorts 2BPK, 2BOMSCh-Bl, 2BOBSCh-B2 in complex with stabilizing and plasticizing additions NaOH, Ca(OH)2, SAS and by mazut modification was elaborated. It was shown that heating capacity of WCFS based on sort of 2BPK. make 2900 kcal/kg (12,2 MJ/kg), and it is increased as well as values of sedimentation stability and fluidity of WCFS at them modifying with mazut, stabilizers and plasticizing agents.
3. The correlation dependence of the main colloid-chemical parameters of WCFS was established rheological characteristics from physic-chemical properties of coal (ash content, water-absorbing capacity, heating capacity, volatile matter content, carboxylic and hydroxyl groups) their quantity in the fuel suspension, dispersion degree, stabilizing additions, and pH of dispersion medium. It was shown that in processed fuel suspension by established optimal quantity of stabilizing and plasticizing additions NaOH, Ca(OH)2, and SAS their values as stability, viscosity and fluidity are kept constant.
4. It was determined that structural viscosity of WCFS obtained based on brown coals is higher (2.52 MPa s in suspension obtained from brown coal sort of 2BPK.) than obtained based on black coal (1.84 MPa s in suspension obtained from black coal sort of 1SSK.OM) that connected enough with high of carboxylic and hydroxyl groups content in the macromolecules of brown coals.
5. It was established that at addition of NaOH, Са(ОН)г stabilizers in the range 0.5-2.0% from weight of fuel, its rheological parameters is practical constant with time; the structural viscosity of WCFS is decreased more than in 1.5-2.0 times, and dynamical strain of displacement is increased in 2 times at rising of temperature from 20°C to 60°C respectively.
6. It was shown the structural viscosity and stability of WCFS dependence on content in it the fraction of solid phase with size of particles is less than 50 pm. The values indicated suspension parameters are enhanced with increasing the content this fraction in the total mass of coal. Moreover, the suspension with optimal of viscosity values and stability are formed at content this fraction is not more than 80% in coal mass can be reached by regulation of grinding time of coal. It is found that the solid phase content is 38-40, 44-46, 49-51 and 52-55% respectively in the obtained coals based on 2BPK, 2BOMSCh-Bl, 2BOMSCh-B2, and 1SSKOM.
7. It was shown possibility of combustion of obtained stabilized WCFS in furnace aggregates with using new jumbo burner. It was determined that the process them combustion is characterized by high full burning of coal (98.0-99.7%) should be said with known mention the effect oxygen containing in the dispersion medium of fuel plays role as intermediate oxidizing agent at all stages itself combustion. In addition oxygen activates surface on the solid phase of fuel. The result burning of its sputtered particles is began but this fact is not carried out by combustion of coal-volatile matter, it is performanced on the surface where heterogenic reaction of oxidizing formed. It was determined WCFS with normal rheological properties can be obtained at using is not only main water with hardness 2.5 mg-eq./l) and also it meets requirements of LPC (limited permissible concentration) of industrial sewage (4.4 mg-eq./l) which is more reasonable and economically benefit.
8. Technological schedule, and instructions of obtaining and combustion of WCFS based on brown and black coals of Uzbekistan are developed, experimental - industrial tests (from 18.07.2013 to 20.07.2013 and from 14.11.2014 from 17.11.2014) of obtained WCFS at their combustion in furnace of driving chamber of Angren were carried out and at this economical effect at substitution of mazut on proposed in this dissertation WCFS has been equaled 291,6 ml. sum per year, only without the depreciation charges. It is shown that at substitution of existing types of fuels at present (mazut, natural gas and other) on WCFS at enterprises of stock company «Almalyk МСС», then in industrial scale at state stock company «Uzbekenergo», economic performance is sufficient increased. WCFS obtained is recommended as alternative fuel for wide application on a number of heat and power aggregates, agricultural and communal spheres of Uzbekistan.