H.U.T.

Experience

Engro Fertilizers

Chemical and Process Engineering Intern · Summer 2016 · Daharki, Sindh, Pakistan

At Engro Fertilizers, I studied the ammonia synthesis loop. I used Aspen HYSYS, a process simulation program, and the plant's own operating data. I also worked on cooling-tower performance and equipment warranty claims. The internship taught me a habit I still use. Compare the model with what the plant is really doing. Then use the gaps to make an operating decision.

model against plant data gaps where they disagree points at equipment checked on the plant, then the model is updated
The model is compared with the plant. Where they disagree points at a piece of equipment. The check on the plant updates the model.

Cooling-tower system

7%lower energy use
18%lower water use

Measured after the changes were made.

Equipment warranty claims

$0.4M+

Capital and operating savings. The claims also helped restore production capacity.

The ammonia loop

Hydrogen and nitrogen do not all react in one pass. The gas that did not react goes back around the loop. Argon and methane do not react at all, so they build up. A purge removes them. But the purge also takes some hydrogen with it. I led an Aspen HYSYS analysis of the loop, using the plant's operating data. The work helped find equipment faults and put a cost on each one. That gave the operations team a clearer basis for troubleshooting.

fresh H₂ + N₂ Compressor circulator Converter catalyst bed Cooling ammonia condenses Separator gas above, liquid below unreacted gas returns, argon and methane go with it purge, to recovery or fuel more purge: fewer inert gases, more hydrogen lost less purge: inert gases build up, the loop works harder liquid ammonia, the product
  1. Fresh hydrogen and nitrogen join recycled gas.
  2. The gas goes through the compressor and then the converter, where ammonia forms.
  3. Cooling turns the ammonia into a liquid. The separator sends the liquid out as the product.
  4. The gas that is left goes back around the loop. A small purge removes the argon and methane that build up.
Purge gas goes to recovery or is used as fuel. It also carries some hydrogen away.

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Most of the unreacted gas goes back to the converter. A small purge stops argon and methane from building up. Some usable hydrogen leaves with the purge.
Aspen HYSYS model what the loop should do at these conditions Plant operating data what the loop was actually doing Where they disagree a flow, pressure or temperature that does not fit One piece of equipment the fault that would explain the gap compared, condition by condition the gaps are the finding a gap points at something specific checked on the plant, then the model is updated cost impact, then an operating decision
  1. The Aspen HYSYS model says what the loop should be doing at the plant's conditions.
  2. The plant's operating data says what the loop was really doing.
  3. Where the two disagree, one reading does not fit: a flow, a pressure or a temperature. That gap points at one piece of equipment.
  4. The idea is checked on the plant. Then the model is updated.
The operations team then decides what to do, based on the cost of each gap.

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The model is not the answer. It is the thing you compare the plant with, so the gaps show. Each gap points at one piece of equipment. That is checked on the plant. The cost of the gap is what the operations team decides on.

The cooling towers

I reviewed four things in the cooling-tower system: approach and range, fouling in the heat exchangers, the fans and pumps, and cycles of concentration. Approach and range mean how much the water cools in the tower, and how close it gets to the lowest temperature the air can give. Fouling is scale and dirt on the heat-exchanger surfaces. Cycles of concentration is set by how much water is drained and replaced. It decides how concentrated the minerals get. Changes from this work cut energy use in the cooling-tower system by 7% and water use by 18%. Both numbers were measured after the changes were made.

warm, moist air out air in spray header fill basin P pump cool water Process heat exchanger picks up the plant's heat warmer water returns to the tower make-up water in blowdown out 1 2 3 3 4 1 approach and range 2 exchanger fouling 3 fans and pumps 4 cycles of concentration, set by how much is drained and replaced
  1. Cool water leaves the basin at the bottom of the tower. A pump moves it on.
  2. In the heat exchanger, the water picks up heat from the plant.
  3. The warm water goes back to the top of the tower. It falls through the fill and cools as some of it evaporates.
Make-up water comes into the basin to replace what was lost. Blowdown is water drained from the basin. It takes the built-up minerals out.

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The water picks up heat in the exchanger. It goes back to the tower and cools as some of it evaporates. Blowdown drains water to remove the built-up minerals. Make-up water replaces what was lost. The numbers show where the four things I reviewed sit in the loop. They do not show which change produced which result.

Warranty recovery

I also negotiated equipment warranty claims. The claims secured $0.4M+ in capital and operating savings combined. They also helped restore production capacity.

Equipment under-performs Documented against the supplier's specification Claim raised with the supplier Negotiated scope and remedy Outcome capital and operating savings, production capacity restored
  1. A piece of equipment does not perform as it should.
  2. Its real performance is written up next to what the supplier promised in the specification.
  3. A claim is raised with the supplier.
  4. The two sides negotiate what the claim covers and how the supplier will put it right.
  5. Outcome: capital and operating savings, and production capacity restored.

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A warranty claim is an argument made with the supplier's own numbers. Most of the work is in the second step, the write-up.

What I learned

At Engro, a model was useful when it helped the team find one specific problem and check whether a fix worked. I kept that habit. It later shaped how I worked on membrane products and data-center cooling.