Technical and cost assessment of energy efficiency improvement and greenhouse gas emission reduction potentials in Thai cement industry

The cement industry is one of the most energy-consuming industries in Thailand, with high associated carbon dioxide (CO₂) emissions. The cement sector accounted for about 20.6 million tonnes of CO₂ emissions in 2005. The fuel intensity of the Thai cement industry was about 3.11 gigajoules (GJ)/tonne cement; the electricity intensity was about 94.3 kWh/tonne cement, and the total primary energy intensity was about 4.09 GJ/tonne cement in 2005 with the clinker to cement ratio of around 82%. In this study, the potential application of 47 energy-efficiency measures is assessed for the Thai cement industry. Using a bottom-up electricity conservation supply curve model, the cost-effective electricity efficiency improvement potential for the Thai cement industry is estimated to be about 265 gigawatt hours (GWh), which accounts for 8% of total electricity use in the cement industry in 2005. Total technical electricity-saving potential is 1,697 GWh, which accounts for 51% of total electricity use in the cement industry in 2005. The CO₂ emission reduction potential associated with the cost-effective electricity savings is 159 kilotonne (kt) CO₂, while the total technical potential for CO₂ emission reductions is 902 ktonne CO₂. The fuel conservation supply curve model shows a cost-effective fuel-efficiency improvement potential of 17,214 terajoules (TJ) and a total technical fuel efficiency improvement potential equal to 21,202 TJ, accounting for 16% and 19% of the total fuel use in the cement industry in 2005, respectively. CO₂ emission reduction potentials associated with cost-effective and technical fuel-saving measures are 2,229 ktonne and 2,603 ktonne, respectively. Sensitivity analyses were conducted for discount rate, electricity and fuel prices, and exchange rate that showed the significant influence of these parameters on the results. Hence, the results of the study should be interpreted with caution.     

A Case History on Underpinning for a Distressed Building on Hard Residual Soil Underneath Non-Uniform Loose Sand

This paper presents a case history on the failure of Suranivet 9, a student dormitory in the campus of Suranaree University of Technology (SUT), Thailand. The dormitory encountered excessive differential settlement due to the variation in soil profile. Part of the building was underlain by very stiff to hard SUT silty clay and part by loose clayey sand. Underpinning to extend the foundations down to stable stratum was employed to strengthen bearing capacity and minimize settlement. The underpinning design and procedure were summarized. In practice, the static formula was used for the preliminary micro-pile design (selection of pile section and length for different loads and soil profiles). The undrained shear strength (S_u) of SUT silty clay was approximated using the Stress History and Normalized Soil Engineering Properties (SHANSEP) technique and standard penetration number (N). The finite element method was employed to predict the load-settlement curve of the micro-pile. Modified cam clay model was proved as a suitable model for this prediction. The measured settlements of the underpinned foundations after one year service were less than 0.5 mm. This small settlement guarantees the stability of the underpinned structure. It is also found that the settlement ratio (ratio of the measured settlement of underpinned foundations to the predicted settlement of single micro-pile) varied from 0.7 to 3.0.     

MATHEMATICAL MODEL DEVELOPMENT AND SIMULATION OF HEAT PUMP FRUIT DRYER

ABSTRACT

A mathematical model of a heat pump fruit dryer was developed to study the performance of heat pump dryers. Using the moisture content of papaya glace' drying, the refrigerant temperature at the evaporator and condenser and the performance, was verified. It was found that the simulated results using closed loop heat pump dryer were close to the experimental results. The criteria for evaluating the performance were specific moisture extraction rate and drying rate. The results showed that ambient conditions affected significantly on the performance of the open loop dryer and the partially closed loop dryer. Also, the fraction of evaporator bypass air affected markedly on the performance of all heat pump dryers. In addition, it was found that specific air flow rate and drying air temperature affected significantly the performance of all heat pump dryers.     

Potential for power generation in a large white rice mill

An energy analysis was conducted on the steam power plant of a large white rice mill. The boiler fired by paddy husk raised steam for a steam engine coupled to a generator. Additional electricity was imported to meet the total demand of the mill. Potentials for power generation are assessed on two alternative systems namely the boiler and turbine system and the gasifier and internal combustion engine system. Both cases of husk-match and power-match are considered. For the case of power-match, both alternative power generation systems are economically feasible.     

DIFFUSION MODELS OF PAPAYA AND MANGO GLACe’ DRYING

ABSTRACT

The objective of this research was to develop diffusion models for papaya and mango glace’ drying. Effective diffusion coefficients of papaya and mango glace’ were evaluated by regression analysis of the experimental data to drying kinetic equation. Models 1 and 2 were developed by assuming that effective diffusion coefficients were constant and varied proportionally with the moisture ratio. Model 3, which the Arrhenius factor was a second-degree polynomial function of moisture content, was developed by assuming that the value of effective diffusion coefficient was constant over a short time interval. Model 4, which was similar to Model 3, was developed by considering the effect of volume shrinkage during drying. Four diffusion models were compared and it was found that the predicted values of moisture contents calculated by using Models 1 and 2 were close to experimental values during the early period of drying. Models 3 and 4 were able to have better predictions particularly towards the final period of drying. However, Model 4 was complicated. Therefore, Model 3 was recommended for calculating drying curves of papaya and mango glace’ drying.     

EFFECT OF TEMPERING ON SUBSEQUENT DRYING OF PADDY USING FLUIDISATION TECHNIQUE

Drying and tempering models for paddy drying by a fluidised bed technique have been developed to describe the moisture movement inside a single paddy kernel. The grain shape was considered as a finite cylinder. The internal diffusion is an important contribution to control the drying rate of paddy. The dependence of effective diffusion coefficient on drying temperature can be adequately explained based on Arrhenius form. The parameters of this equation were evaluated in the range of temperatures between 110°C and 170°C by using the regression analysis with 189 experimental drying data. As compared with no tempering, the faster drying rate can be obtained by tempering treatment between drying stages. The effect of degrees of tempering on determining the moisture reduction in the second stage has also been explored. According to the simulation results, a prediction equation of the required tempering time for the tempering index of 0.95 has been established in which the drying air temperature, initial moisture content and drying time are taken into account. The tempering time for 35 min is recommended for the continuous fluidised bed dryers being operated in rice mills.     

DIFFUSION MODELS OF PAPAYA AND MANGO GLACe' DRYING

The objective of this research was to develop diffusion models for papaya and mango glace' drying. Effective diffusion coefficients of papaya and mango glace' were evaluated by regression analysis of the experimental data to drying kinetic equation. Models 1 and 2 were developed by assuming that effective diffusion coefficients were constant and varied proportionally with the moisture ratio. Model 3, which the Arrhenius factor was a second-degree polynomial function of moisture content, was developed by assuming that the value of effective diffusion coefficient was constant over a short time interval. Model 4, which was similar to Model 3, was developed by considering the effect of volume shrinkage during drying. Four diffusion models were compared and it was found that the predicted values of moisture contents calculated by using Models 1 and 2 were close to experimental values during the early period of drying. Models 3 and 4 were able to have better predictions particularly towards the final period of drying. However, Model 4 was complicated. Therefore, Model 3 was recommended for calculating drying curves of papaya and mango glace' drying.     

Chiral separation using a novel combination of cooling crystallization and a membrane barrier: Resolution of DL-glutamic acid

Chiral separation of racemic mixtures is essential in the production of many pharmaceutical compounds. The present work describes a novel chiral separation technique that combines cooling crystallization and a membrane separation that is used in DL-glutamic acid resolution. The process utilizes two crystallization chambers that are separated by a membrane that prevents transport of crystals from one chamber to another. Importantly, conditions must be controlled so that only a pure species crystallizes in each of the chambers. This is done by appropriate addition of seed crystals to each chamber and by restricting the formation of new crystals to secondary nucleation mechanisms. The seed crystals may grow or participate in secondary nucleation, but conditions must be controlled so as to prevent primary nucleation, which would result in the formation of both crystal species in each chamber. Experiments were conducted with different amounts of seed crystals to determine operating conditions that produce the high product yield and purity. The results show that this novel chiral separation process is promising: the product purity was over 94% (with a separation factor of 16) and the product yield was increased by as much as 56% more than could be obtained with simple cooling crystallization.     

The use of conservation supply curves in energy policy and economic analysis: The case study of Thai cement industry

The cement industry is one of the largest energy-consuming industries in Thailand with high carbon dioxide (CO₂) emissions. Using a bottom-up electricity Conservation Supply Curve (CSC) model, the cost effective and the total technical electricity-efficiency potential for the Thai cement industry in 2008 is estimated to be about 265 and 1697 gigawatt-hours (GWh) which account for 8% and 51% of the total electricity used in the cement industry in 2005, respectively. The fuel CSC model shows the cost-effective fuel-efficiency potential to be 17,214 terajoules (TJ) and the total technical fuel-efficiency potential equal to 21,202 TJ, accounting for 16% and 19% of the total fuel used in cement industry in 2005, respectively. The economic analysis in this paper shows how the information from the CSCs can be used to calculate the present value (PV) of net cost savings over a period of time taking into account the energy price escalation rate. The results from the policy scenario analysis show that the most effective and efficient policy scenario is the introduction of an energy-related CO₂ tax for the cement industry under a voluntary agreement program. This scenario results in 16.9% primary energy-efficiency improvement over a 5-year implementation period.