A process and system for automated online fouling prevention of vertical shell and tube gas-to-gas heat exchangers

A system for on-line prevention of fouling of gas-to-gas heat exchanger wherein the heat exchanger is a shell and tube gas-to-gas heat exchanger having a tube side and shell side, contaminated gas flows through the tube side and clean gas through the shell side, the system comprising:

• a grit injection apparatus,
• a means for measuring gas temperatures, composition and flowrates;
• a control system configured to:
• receive temperature measurements from the means for measuring temperature,
• receive composition measurements from the means for measuring composition,
• receive flowrate measurements from the means for measuring flowrate,
• calculate a heat exchange coefficient from measured temperatures, composition and flowrates of gases in the heat exchanger to obtain a measured heat exchange coefficient;
• comparing the measured heat exchange coefficient to a predetermined heat exchange coefficient;
• and
• if measured heat exchange coefficient is less than the predetermined heat exchange coefficient, signal the grit injection apparatus to add grit to the contaminated gas;
• optionally wherein the means for measuring temperature is a plurality of thermocouples.

A heat exchange system comprising:

• a shell and tube gas-to-gas heat exchanger having a tube side and shell side, wherein hot contaminated gas flows through the tube side and clean gas through the shell side;
• at least one grit injection apparatus, each grit injection apparatus comprising a distribution and pressure charging hopper operatively connected to a main hopper and a mechanical pressurization means or pressurizing gas line;
• at least one vertical pipe extending from the distribution and pressure charging hopper;
• wherein the distribution and pressure charging hopper and at least one vertical tube are configured to be pressurized;
• and
• a grit outlet pipe operatively connected to the at least one vertical pipe and extending into an upper plenum of a heat exchanger;
• wherein the grit injection apparatus is configured to provide pressurized grit to the upper plenum;
• a means for measuring gas temperatures, composition and flowrates;
• a control system configured to:
• receive temperature measurements from the means for measuring temperature,
• receive composition measurements from the means for measuring composition,
• receive flowrate measurements from the means for measuring flowrate,
• calculate a heat exchange coefficient from measured temperatures, composition and flowrates of gases in the heat exchanger to obtain a measured heat exchange coefficient;
• comparing the measured heat exchange coefficient to a predetermined heat exchange coefficient;
• and
• if measured heat exchange coefficient is less than the predetermined heat exchange coefficient, signal the grit injection apparatus to add grit to the contaminated gas.