Fuel saving due to pinch analysis and heat recovery in a petrochemical company

Nowadays, decreasing the amount of natural resources and increasing the price of it, motivates to consider energy conservation as a main concern of many process industries, especially oil, refinery and petrochemical plants. Pinch Analysis (PA) is a powerful method for identifying and selecting technical solution to improve efficiencies and provide an optimum procedure for energy saving. This paper analyses, the effectiveness of applying PA to optimize energy consumption for a given set of process streams in a Petrochemical Company in Iran. In this study, firstly, the interested process streams have been selected, maximum heating and cooling load are computed, and then composite curves have been drawn - by Matlab code - which provides a visual profile of the availability of heating or cooling from the process streams. Secondly, the cost of recovered heat is computed in terms of fuel saving, which confirms applying PA could save significant amount of fuel expenses for the company. Finally, the corresponded Heat Exchanger Network (HEN) has been designed, and the investment costs for heat exchangers have been computed in order to find out payback time of the investment costs which is approximately 17 months for this case study

Bilateral Angle-Closure Glaucoma in a Young Female Receiving Cabergoline: A Case Report

Purpose: To report a case of bilateral acute angle-closure glaucoma after oral administration of cabergoline for the treatment of galactorrhea. Methods: A diagnosis of secondary drug-induced angle-closure glaucoma was made in a patient with elevated intraocular pressure (IOP) and myopic refractive shift, which was confirmed by ultrasound biomicroscopy (UBM) of the ciliary body and anterior segment, sonography, and optical coherence tomography. The treatment included the discontinuation of the culprit drug and the administration of topical anti-glaucoma drops. The treatment course was followed with serial measurements of the IOP and refraction, and with performing UBM. Results: Five hours after he received a single 0.5-mg oral cabergoline tablet, the patient suffered from acute secondary angle-closure glaucoma and myopic refractive error. UBM demonstrated both effusion of the ciliary body and an anterior rotation of the iris-ciliary body. IOP was reduced 8 h after cessation of the causative agent and administration of anti-glaucoma drops. Refractive errors returned to normal levels after 8 days. Conclusion: Secondary acute angle-closure glaucoma has been reported to occur after the administration of some drugs. In this report, an attempt has been made to describe this adverse reaction after oral cabergoline intake

Cornea Collagen Cross-linking for Keratoconus: A Comparison between Accelerated and Conventional Methods

Background: Keratoconus is a progressive degenerative disorder of the cornea in which structural changes in the cornea cause it to become thin and conical in shape. Recently, collagen cross-linking (CXL) has been introduced as an effective intervention in management of progressive keratoconus. Accelerated CXL is a new protocol of this procedure which reduces corneal ultraviolet irradiation exposure time to 5 min. This study aimed to compare visual acuity, keratometry and topographic criteria of keratoconic eyes after conventional and accelerated CXL with a six-month follow-up. Materials and Methods: In this prospective interventional study we assessed eyes of 40 patients. Patients were divided into two groups randomly. One group underwent accelerated (5 min) CXL and the other underwent conventional (30 min) CXL. Visual acuity, topographic criteria and keratometry were assessed preoperatively and 6 months postoperatively. Results: In the present study we assessed 40 patients, 50% of which were right eye (OD) and 50% were left eye (OS). Mean age of patients in the accelerated group was 22.10 and in the conventional group was 22.80 years. Our results showed no significant differences between visual acuity, keratometric and topographic criteria in the two groups before intervention. Likewise our results manifested no significant difference between visual acuity, keratometric, refractive and topographic criteria after intervention. Conclusion: According to our survey topographic criteria and keratometry improvement in the accelerated and conventional protocol are the same. So accelerated protocol is suggested as a safe and effective option for management of progressive keratoconus

Corneal haze and visual outcome after collagen crosslinking for keratoconus: A comparison between total epithelium off and partial epithelial removal methods

Background: Keratoconus is an asymmetric, bilateral, progressive noninflammatory ectasia of the cornea that affects approximately 1 in 2000 of the general population. This may cause a significant negative impact on quality of life. Corneal collagen crosslinking (CXL) is one of the recently introduced methods that have been used to decrease the progression of keratoconus, in particular, as well as other corneal-thinning processes. Materials and Methods: A total of 44 keratoconic eyes of 22 patients were enrolled in this randomized prospective study, after obtaining informed consent. In the first group, the corneal epithelium were totally removed and in the second group, the central 3 mm of epithelium was kept intact and partial removal was performed. After collagen crosslinking in both groups, comprehensive ophthalmologic examination was performed on all patients before and 6 months after the surgery. This article is registered at www.clinicaltrial.gov with registration number NCT01809977. Results: The difference between the two groups was not statistically significant regarding postoperative corneal haziness, refraction, and visual acuity (P > 0.05). However, comparison of pre- and postoperative parameters within each group revealed that total removal of the cornea has resulted in significant improvement of K-max (P value: 0.01) and Q-value (P value: 0.009); while eyes in partial removal group had better improvement of corrected vision (P value: 0.006). Both methods had significant and similar increase in optical corneal density (P < 0.0001). Conclusion: In our study, keeping the central corneal epithelium intact was not beneficial for decreasing corneal haziness, however, this method caused better improvement in corrected vision. Total epithelium off technique resulted in better improvement of K-max and Q-value

Comparison of standard and low dose intraoperative mitomycin c in prevention of corneal hazeafter photorefractive keratectomy

Background: This study aimed to compare two doses of Mitomycin C in reducing haze formation after photorefractive keratectomy. Methods: 170 eyes of 85 patients enrolled; in each patient one eye randomly assigned to be treated by low dose intraoperative MMC (LDMMC) and other eye by standard dose MMC (SDMMC). Then the patients were followed up to 6 months and refraction, Uncorrected Distant Visual Acuity (UCDVA), Best Corrected Distant Visual Acuity (BCDVA) and haze formation submitted in each postoperative exam. Results: The mean preoperative refraction in LDMMC eyes was -3.08 (SD 1.65) sphere and 0.92 (SD 0.88) cylinder. These values for SDMMC eyes were -3.25 (SD 1.80) sphere and 0.81 (SD 0.84) cylinder. Mean postoperative sphere in LDMMC group was -0.132 (SD 0.503) and -0.138 (SD 0.484) in 3 and 6 months after PRK. These results was -0.041 (SD 0.501) and -0.076 (SD 0.489) for SDMMC group. Mean postoperative cylinder 3 and 6 month after PRK was 0.435 (SD 0.218) and 0.423 (SD 0.255). In LDMMC group and 0.435 (SD 0.247) and 0.426 (SD 0.261) in SDMMC group. In third month 14 eyes in LDMMC group presented with grade 1 score of clinical haze. From these eyes only 2 still had this haze after 6 month. 7 eyes in SDMMC group had grade 1 clinical haze at third month- but no clinical haze was seen at the end of 6 th month. Conclusion: The results of the two doses of Mitomycin C were not significant. We suggest to use the lower dose to reduce its side effects

The effect of pterygium surgery on wavefront analysis

Background: Pterygium is a common disorder of the ocular surface. It causes vision impairment -usually irregular type astigmatism- through different mechanisms. In addition, it is believed that surgical excision of the pterygium improves visual problems. The appropriate method to investigate irregular astigmatism is using wavefront analysis. This study was aimed to evaluate wavefront analysis pre and post pterygium surgery. Materials and Methods: This study was performed on 32 patients who underwent surgical excision of pterygium in January 2012. Data were recorded and compared after pre and postoperative comprehensive ophthalmologic examinations including uncorrected and best corrected visual acuity, Orbscan, wavefront analysis and autorefraction to figure out the effects of surgery on different parameters. Results: Comparison of pre and postoperative parameters showed that surgical treatment of the pterygium improves numerous parameters significantly including uncorrected and best corrected visual acuity, spherical and cylinder refractive error, higher order aberration, quadrafoil (Z440), corneal astigmatism and 3 and 5 mm central zone corneal irregularity (all P-values < 0.0001). In addition, it improves vertical coma (P:0.003) and secondary astigmatism (Z420) (P:0.004). Conclusion: It is concluded that surgical excision of the pterygium improves visual acuity, refractive errors and most of the corneal topographic indices and wavefront analysis parameters

Topographic corneal changes after collagen cross-linking in patients with corneal keratoconus

Background: Corneal collagen cross-linking with riboflavin, also known as collagen cross-linking (CXL), involves the application of riboflavin solution to the eye that is activated by illumination with ultraviolet A (UVA) light. We survey here the topographic corneal changes one year after CXL in patients with corneal keratoconus. Materials and Methods: This prospective randomized clinical trial study comprised 66 patients with progression of keratoconus during one year who were enrolled at Feiz University Referral Eye Center in Isfahan. Before and after the operation, patients were examined with slit lamp and funduscopic examinations and measurement of uncorrected visual acuity (UCVA), and best spectacle-corrected visual acuity (BSCVA) was done with a logarithm of minimal angle of resolution (logMAR) scale. Corneal topographic and pachymetry values were derived from Orbscan II. The paired t-test test was used for statistical analyses with SPSS software version 20 (SPSS Inc., Chicago, IL, USA). Results: All 66 patients completed postoperative follow-up at 12 months. The mean age of the patients was 22.4 ± 5.4 years (range: 18-29 years). Thirty-six (54.55%) subjects were men and 30 (45.45%) were women. The mean preoperative sphere was −2.66 ± 2.14 diopter (D), the mean cylinder was −3.97 ± 2.29, and the mean spherical equivalent (SE) was −4.64 ± 2.56. Postoperatively, the mean sphere was −2.22 ± 2.57 D, the mean cylinder was −3.60 ± 2.40 D, and SE was −4.02 ± 2.93 D (P = 0.037). SE also demonstrated a mean difference of 0.62 ± 0.37 D significantly (P = 0.006).The mean diameter of preoperative posterior best-fit sphere (BFS) was 6.33 ± 0.35mm (range: 5.51-7.73 mm) before operation, and it improved to 6.28 ± 0.34mm (range: 4.36-6.13 mm) after operation; the difference was significant (P = 0.039). Conclusion: Our study showed a significant improvement in topographic corneal changes and refractive results in patients with corneal ectasia after CXL

Short-term result of collagen crosslinking in pellucid marginal degeneration

Background: To evaluate effectiveness of collagen crosslinking in pellucid marginal degeneration patients. Materials and Methods: Twenty-one eyes of 15 patients treated by collagen crosslinking were enrolled in our non-controlled clinical trial study. After evaluation of patients about inclusion and exclusion criteria, preoperative examination was done and then patients underwent CXL procedure and seen 6 months after surgery for postoperative examinations. Results: Mean preoperative LogMar uncorrected visual acuity (UCVA) was 0.63 (SE = 0.08), and mean preoperative LogMar BCVA was 0.26 (SE = 0.04). At 6 months postoperative, mean LogMar UCVA was 0.59 (SE = 0.06) and mean LogMar BCVA was 0.19 (SE = 0.02). The non-parametric test (Wilcoxon) showed reduction of LogMar BCVA was significant (P value = 0.02), but reduction of LogMar UCVA was not significant (P value = 0.5). Mean preoperative K1 was 42.23 ± 2.85 and mean postoperative K1 significantly decreased to 41.68 ± 2.44 (P value = 0.008). Also, mean preoperative K2 was 48.39 ± 2.37 and mean postoperative K2 significantly reduced to 47.64 ± 2.16 (P value = 0.002). Conclusion: Most remarkable findings of our study were improvement of visual acuity and reduction K1 and K2 parameters. Stability of other values and absence of detectable change after study period implies halting of the progression of the disease. We suggest CXL can be useful for management of PMD, but we need more studies with larger sample size and longer follow up

Comparative study of two silicone hydrogel contact lenses used as bandage contact lenses after photorefractive keratectomy

Background: Silicon hydrogel bandage contact lenses are used to enhance epithelial healing, control surface-generated pain, and prevent epithelial erosions after refractive surgery. Considering the importance of faster reepithelialization in preventing complications of photorefractive keratectomy (PRK) and the fact that the features and specifications of these commercially-available lenses are different and their performance as a postoperative bandage lenses would be different also, the aim of this study was comparison the efficacy of senofilcon A and lotrafilcon A after PRK. Methods: In this prospective study, 44 patients with PRK in both eyes randomly received a silicon hydrogel contact lens of senofilcon A in one eye and lotrafilcon A in other eye. Then the epithelial defect size, visual acuity and subjective level of pain and discomfort were measured for both eyes and compared on day 1, 3 and 5 postoperatively. Results: There was no statistical difference in rate of reepithelialization between senofilcon A and lotrafilcon A (P > 0.05). The mean pain and discomfort index was significantly lower in eyes with senofilcon A (P 0.05). Conclusion: Silicon hydrogel BCLs are safe and effective for corneal reepithelialization and have great therapeutic outcome on visual outcomes after PRK. But, senofilcon A had better effect on postoperative pain and discomfort which made it superior than lotrafilcon A. However for more conclusive results, it is recommended to study larger sample size with evaluation the possible factors responsible for the obtained findings regarding postoperative pain and discomfort