A Comparative Study of Applying Active-Set and Interior Point Methods in MPC for Controlling Nonlinear pH Process

A comparative study of Model Predictive Control (MPC) using active-set method and interior point methods is proposed as a control technique for highly non-linear pH process. The process is a strong acid-strong base system. A strong acid of hydrochloric acid (HCl) and a strong base of sodium hydroxide (NaOH) with the presence of buffer solution sodium bicarbonate (NaHCO3) are used in a neutralization process flowing into reactor. The non-linear pH neutralization model governed in this process is presented by multi-linear models. Performance of both controllers is studied by evaluating its ability of set-point tracking and disturbance-rejection. Besides, the optimization time is compared between these two methods; both MPC shows the similar performance with no overshoot, offset, and oscillation. However, the conventional active-set method gives a shorter control action time for small scale optimization problem compared to MPC using IPM method for pH control

CFD analysis chlorine gas dispersion in indoor storage: temperatures with wind velocities effect studies

Most of the industrial chemical products encounter natural environmental risk in the process. The indoor release of hazardous dense gases is especial topic for discussion nowadays because the clouds of heavier gases have a tendency to stay near the ground level, causing fatal and injuries the people. In this article a computational fluid dynamics (CFD) code FLUENT was employed in order to model the accidental indoor dispersion of chlorine from a small undetected leak in an indoor industrial space. The results of simulation represented that the chlorine gas spread would behave like liquid and flows on the floor, also the concentration of chlorine increased to above the ground level slowly. The effects of various temperatures and wind velocities on dispersion of heavier gas will help to better identify the potential risks. In this paper, the effects of the environmental situations with the release and spread of chlorine in the indoor space were meticulously examined

A Study on Zeolite Performance in Waste Treating Ponds for Treatment of Palm Oil Mill Effluent.

Oil palm currently occupies the largest acreage of farm land in Malaysia. In 2011, the production of palm oil in Malaysia was recorded as 19.8 million tons which has led to a huge amount of wastewater known as palm oil mill effluent (POME). This work focuses on the ponding system which acts as wastewater treatment plant in order to treat POME. The conventional ponding system applied in mills consists of a series of seven ponds. The maintenance costs of the pond are expensive thus study of alternative methods is needed. POME treatment using zeolite shows a potential to overcome the problem. Samples collected from selected ponds are tested and analyzed using water analyzer method. Result from adsorption by zeolite shows a significant reduction of COD, BOD, Fe, Zn, Mn and turbidity. This shows that zeolite is highly potential to be applied as adsorbent in the POME treatment plants. The results here may lead to lower maintenance cost, lower quantity of treatment ponds and lesser land occupied for the treatment of POME in Malaysia

Effect of high pressurized sterilization on oil palm fruit digestion operation

Sterilization and digestion are two important steps in the palm oil milling process prior to oil extraction. After sterilization, palm fruitlets are stripped and then fed into a digester where the fruitlets are heated with atmospheric pressure steam to soften and loosen the mesocarp fiber. The effect of different pressures of sterilization on digestion operation needs to be investigated. To convey better understanding of the process, several tests were performed on the fruitlets sterilized under different sterilization conditions, i.e., 40 and 70 psi. Oil released, sludge formation and water absorption during the digestion process were analyzed. It was found that fruitlets sterilized at 70 psi contained more sugar content in the condensate due to more hydrolyzed sterilized fruit. It was also found that fruit sterilized at higher pressure released more oil into the condensate and absorbed more water

Automation of anaesthesia: a review on multivariable control

Anaesthesia is a multivariable problem where a combination of drugs are used to induce desired hypnotic, analgesia and immobility states. The automation of anaesthesia may improve the safety and cost-effectiveness of anaesthesia. However, the realization of a safe and reliable multivariable closed-loop control of anaesthesia is yet to be achieved due to a manifold of challenges. In this paper, several significant challenges in automation of anaesthesia are discussed, namely model uncertainty, controlled variables, closed-loop application and dependability. The increasingly reliable measurement device, robust and adaptive controller, and better fault tolerance strategy are paving the way for automation of anaesthesia

Computer modelling of phase change materials using the orthogonal collocation method

A computer program had been developed for aone-dimensional, orthogonal collocation model of a packed bed heat storage system. The system comprised of a cylindrical storage tank filled with phase change material (PCM) encapsulated in spherical containers. This paper also presented the thermal performance simulation of packed bed heat storage system using PCM during charging and discharging process. Paraffin wax was chosen as PCM, and air was chosen as heat transfer fluid (HTF).The enthalpy method was used in the model to accommodate the phase change behaviour of PCM over a range of temperature. It was shown that the governing equations were two energy conservation equations written for HTF and PCM. Both governing equations were numerically solved by applying orthogonal collocation approach implemented using MATLAB. The results obtained by solving the model using the orthogonal collocation method were initially validated with experimental results in the literature. The model covered through-flow conditions for charging and discharging the thermal heat storage within the air. In this paper, the complete computational model was simplified and efficient enough to interface with a larger program simulating a heat storage system. The simulations were conducted in order to derive the temperature profiles of HTF and PCM as well as to estimate the time required to complete charging and discharging of PCM

Multiple model predictive control of nonlinear pH neutralization system

In this paper the control of nonlinear systems using linear models is studied. The control strategy utilizes a piecewise linear description of the process, considered the model bank. The model bank is then combined at each sampling interval, through the application of a Bayesian weight calculator, to render a single linear model describing the system. The linear model is used in a model predictive control (MPC) setting to render the optimal control move. The performance of the setup is simulated for a pH neutralization process, which demonstrates a good following of setpoint changes and quick reduction of oscillations

Effect of microwave-assisted acid or alkali pretreatment on sugar release from dragon fruit foliage

Agriculture residues are a promising feedstock for value-added products from lignocellulosic waste. However, pretreatment of lignocellulosic materials is essential to facilitate enzymatic hydrolysis and improve sugar yield. The objective of this study is to evaluate the effect of acid or alkali during microwave-assisted pretreatment of dragon fruit foliage (DFF) that would make hydrolysis process more efficient. In the present study, distilled water and three chemicals were examined for their effects on releasing monomeric sugar during microwave treatment. Microwave-assisted pretreatment namely microwave-distilled water (M-H2O) (control); microwave-sulfuric acid (M-H2SO4); microwave-sodium hydroxide (M-NaOH); and microwave-sodium bicarbonate (M-NaHCO3) pretreatment were performed using 5% (w/v) of DFF as substrate at 800 watt microwave power for 5 minutes exposure time. Highest yield of monomeric sugar was found at 15.56 mg/g using M-NaOH pretreatment at 0.1N NaOH. For M-H2SO4 pretreatment, 0.1N H2SO4 produced 8.2 mg/g of monomeric sugar. Application of M-NaHCO3 pretreatment using 0.05N NaHCO3 solution released 6.45 mg/g of monomeric sugar. While, soaking DFF in distilled water and subjecting to microwave irradiation released 6.6 mg/g of monomeric sugar. Treatments with the lowest concentration (0.01 N) of the three chemicals released only small quantities of total monomeric sugars and less than that with distilled water. The changes in the physical structure of DFF prior to and after the microwave-assisted pretreatment are also reported

Low-temperature dilute acid hydrolysis of oil palm frond

Oil palm frond (OPF) fiber, a lignocellulosic waste from the palm oil industry, contains high cellulose and hemicellulose content, thus it is a potential feedstock for simple sugars production. This paper describes the two-stage hydrolysis process focusing on the use of low-temperature dilute acid hydrolysis to convert the hemicellulose in OPF fiber to simple sugars (xylose, arabinose, and glucose). The objective of the present study was to evaluate the effect of operating conditions of dilute sulfuric acid hydrolysis undertaken in a 1 L self-built batch reactor on xylose production from OPF fiber. The reaction conditions were temperatures (100–140°C), acid concentrations (2–6%), and reaction times (30–240 min). The mass ratio of solid/liquid was kept at 1:30. Analysis of the three main sugars glucose, xylose, and arabinose were determined using high-pressure liquid chromatography. The optimum reaction temperature, reaction time, and acid concentration were found to be 120°C, 120 min, and 2% acid, respectively. Based on the potential amount of xylose (10.8 mg/mL), 94% conversion (10.15 mg/mL) was obtained under the optimum conditions with small amount of furfural (0.016 mg/mL). To enhance the effectiveness of dilute acid hydrolysis, the hydrolysis of OPF fiber was also performed using ultrasonic-pretreated OPF fiber. The effects of ultrasonic parameters power (40–80%) and ultrasonication times (20–60 min) were determined on sugar yields under optimum hydrolysis conditions (2% acid sulfuric, 120°C and 120 min). However, the use of ultrasonication was found to have detrimental effect on the yield of simple sugars due to the 10-fold increase in the formation of furfural

Microwave-assisted pretreatment of sago palm bark

Three types of microwave-assisted diluted solvents were employed using 0.1 N H2SO4 (MSA), 0.1 N NaOH (MSH), and 0.01 N NaHCO3 (MSB). These solvents were evaluated as possible pretreatment routes for sago palm bark (SPB) with their effects on the pretreated substrate. A variety of analyses, consisting of fiber analysis, energy dispersive X-ray spectroscopy (EDX), X-ray fluorescence spectrometer (XRF), X-ray powder diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscope (SEM), and high-performance liquid chromatography (HPLC), were performed to understand the pretreatment effects on the chemical and physical characteristics of SPB and pretreatment liquor. The thermal analysis has revealed that higher hemicellulose degradation was also found in MSA pretreatment. In the analyses of the pretreatment liquid for the extracted monomeric sugar, a higher amount of glucose was found (9 mg/g) using MSH pretreatment and the highest xylose level was found (4 mg/g) using MSA pretreatment. The analysis of the formation of inhibitors has shown that acetic acid was only found in the MSH pretreatment